8.5.0 (unreleased)#

Other changes:

  • Test against Python 3.12.

8.4.0 (2024-01-07)#


  • Add a new class attribute, empty_value to DelimitedList and DelimitedTuple, with a default of "". This controls the value deserialized when an empty string is seen.

empty_value can be used to handle types other than strings more gracefully, e.g.

from webargs import fields

class IntList(fields.DelimitedList):
    empty_value = 0

myfield = IntList(fields.Int())


empty_value will be changing in webargs v9.0 to be missing by default. This will allow use of fields with load_default to specify handling of the empty value.

  • The rule for default argument names has been made configurable by overriding the get_default_arg_name method. This is described in the argument passing documentation.

Other changes:

  • Drop support for Python 3.7, which is EOL.

  • Type annotations for FlaskParser have been improved.

8.3.0 (2023-07-10)#


  • webargs.Parser now inherits from typing.Generic and is parametrizable over the type of the request object. Various framework-specific parsers are parametrized over their relevant request object classes.

  • webargs.Parser and its subclasses now support passing arguments as a single keyword argument without expanding the parsed data into its components. For more details, see advanced docs on Argument Passing and arg_name.

Other changes:

  • Type annotations have been improved to allow Mapping for dict-like schemas where previously dict was used. This makes the type covariant rather than invariant (#836).

  • Test against Python 3.11 (#787).

8.2.0 (2022-07-11)#


  • A new method, webargs.Parser.async_parse, can be used for async-aware parsing from the base parser class. This can handle async location loader functions and async error handlers.

  • webargs.Parser.use_args and use_kwargs can now be used to decorate async functions, and will use async_parse if the decorated function is also async. They will call the non-async parse method when used to decorate non-async functions.

  • As a result of the changes to webargs.Parser, FlaskParser, DjangoParser, and FalconParser now all support async views. Thanks @Isira-Seneviratne for the initial PR.


  • The implementation of AsyncParser has changed. Now that webargs.Parser has built-in support for async usage, the primary purpose of AsyncParser is to redefine parse as an alias for async_parse

  • Set python_requires>=3.7.2 in package metadata (#692). Thanks @kasium for the PR.

8.1.0 (2022-01-12)#

Bug fixes:

  • Fix publishing type hints per PEP-561. (#650).

  • Add DelimitedTuple to fields.__all__ (#678).

  • Narrow type of argmap from Mapping to Dict (#682).

Other changes:

  • Test against Python 3.10 (#647).

  • Drop support for Python 3.6 (#673).

  • Address distutils deprecation warning in Python 3.10 (#652). Thanks @kkirsche for the PR.

  • Use postponed evaluation of annotations (#663). Thanks @Isira-Seneviratne for the PR.

  • Pin mypy version in tox (#674).

  • Improve type annotations for __version_info__ (#680).

8.0.1 (2021-08-12)#

Bug fixes:

  • Fix “DelimitedList deserializes empty string as ['']” (#623). Thanks @TTWSchell for reporting and for the PR.

Other changes:

  • New documentation theme with furo. Thanks to @pradyunsg for writing furo!

  • Webargs has a new logo. Thanks to @michaelizergit! (#312)

  • Don’t build universal wheels. We don’t support Python 2 anymore. (#632)

  • Make the build reproducible (#631).

8.0.0 (2021-04-08)#


  • Add Parser.pre_load as a method for allowing users to modify data before schema loading, but without redefining location loaders. See advanced docs on Parser pre_load for usage information. (#583)

  • Backwards-incompatible: unknown defaults to None for body locations (json, form and json_or_form) (#580).

  • Detection of fields as “multi-value” for unpacking lists from multi-dict types is now extensible with the is_multiple attribute. If a field sets is_multiple = True it will be detected as a multi-value field. If is_multiple is not set or is set to None, webargs will check if the field is an instance of List or Tuple. (#563)

  • A new attribute on Parser objects, Parser.KNOWN_MULTI_FIELDS can be used to set fields which should be detected as is_multiple=True even when the attribute is not set (#592).

See docs on “Multi-Field Detection” for more details.

Bug fixes:

  • Tuple field now behaves as a “multiple” field (#585).

7.0.1 (2020-12-14)#

Bug fixes:

  • Fix DelimitedList and DelimitedTuple to pass additional keyword arguments through their _serialize methods to the child fields and fix type checking on these classes. (#569) Thanks to @decaz for reporting.

7.0.0 (2020-12-10)#


  • Backwards-incompatible: Drop support for webapp2 (#565).

  • Add type annotations to Parser class, DelimitedList, and DelimitedTuple. (#566)

7.0.0b2 (2020-12-01)#


  • DjangoParser now supports the headers location. (#540)

  • FalconParser now supports a new media location, which uses Falcon’s media decoding. (#253)

media behaves very similarly to the json location but also supports any registered media handler. See the Falcon documentation on media types for more details.


  • FalconParser defaults to the media location instead of json. (#253)

  • Test against Python 3.9 (#552).

  • Backwards-incompatible: Drop support for Python 3.5 (#553).

7.0.0b1 (2020-09-11)#


  • Backwards-incompatible: Remove support for marshmallow2 (#539)

  • Backwards-incompatible: Remove dict2schema

    Users desiring the dict2schema functionality may now rely upon marshmallow.Schema.from_dict. Rewrite any code using dict2schema like so:

import marshmallow as ma

# webargs 6.x and older
from webargs import dict2schema

myschema = dict2schema({"q1", ma.fields.Int()})

# webargs 7.x
myschema = ma.Schema.from_dict({"q1", ma.fields.Int()})


  • Add unknown as a parameter to Parser.parse, Parser.use_args, Parser.use_kwargs, and parser instantiation. When set, it will be passed to Schema.load. When not set, the value passed will depend on the parser’s settings. If set to None, the schema’s default behavior will be used (i.e. no value is passed to Schema.load) and parser settings will be ignored.

This allows usages like

import marshmallow as ma

    {"q1": ma.fields.Int(), "q2": ma.fields.Int()}, location="query", unknown=ma.EXCLUDE
def foo(q1, q2):
  • Defaults for unknown may be customized on parser classes via Parser.DEFAULT_UNKNOWN_BY_LOCATION, which maps location names to values to use.

Usages are varied, but include

import marshmallow as ma
from webargs.flaskparser import FlaskParser

# as well as...
class MyParser(FlaskParser):

parser = MyParser()

Setting the unknown value for a Parser instance has higher precedence. So

parser = MyParser(unknown=ma.RAISE)

will always pass RAISE, even when the location is query.

  • By default, webargs will pass unknown=EXCLUDE for all locations except for request bodies (json, form, and json_or_form) and path parameters. Request bodies and path parameters will pass unknown=RAISE. This behavior is defined by the default value for DEFAULT_UNKNOWN_BY_LOCATION.


  • Registered error_handler callbacks are required to raise an exception. If a handler is invoked and no exception is raised, webargs will raise a ValueError (#527)

6.1.1 (2020-09-08)#

Bug fixes:

  • Failure to validate flask headers would produce error data which contained tuples as keys, and was therefore not JSON-serializable. (#500) These errors will now extract the headername as the key correctly. Thanks to @shughes-uk for reporting.

6.1.0 (2020-04-05)#


  • Add fields.DelimitedTuple when using marshmallow 3. This behaves as a combination of fields.DelimitedList and marshmallow.fields.Tuple. It takes an iterable of fields, plus a delimiter (defaults to ,), and parses delimiter-separated strings into tuples. (#509)

  • Add __str__ and __repr__ to MultiDictProxy to make it easier to work with (#488)


6.0.0 (2020-02-27)#


  • FalconParser: Pass request content length to to provide compatibility with falcon.testing (#477). Thanks @suola for the PR.

  • Backwards-incompatible: Factorize the use_args / use_kwargs branch in all parsers. When as_kwargs is False, arguments are now consistently appended to the arguments list by the use_args decorator. Before this change, the PyramidParser would prepend the argument list on each call to use_args. Pyramid view functions must reverse the order of their arguments. (#478)

6.0.0b8 (2020-02-16)#


  • Backwards-incompatible: Use keyword-only arguments (#472).

6.0.0b7 (2020-02-14)#


  • Backwards-incompatible: webargs will rewrite the error messages in ValidationErrors to be namespaced under the location which raised the error. The messages field on errors will therefore be one layer deeper with a single top-level key.

6.0.0b6 (2020-01-31)#


  • Remove the cache attached to webargs parsers. Due to changes between webargs v5 and v6, the cache is no longer considered useful.

Other changes:

  • Import Mapping from in (#471). Thanks @tirkarthi for the PR.

6.0.0b5 (2020-01-30)#


  • Backwards-incompatible: DelimitedList now requires that its input be a string and always serializes as a string. It can still serialize and deserialize using another field, e.g. DelimitedList(Int()) is still valid and requires that the values in the list parse as ints.

6.0.0b4 (2020-01-28)#

Bug fixes:

  • CVE-2020-7965: Don’t attempt to parse JSON if request’s content type is mismatched (bugfix from 5.5.3).

6.0.0b3 (2020-01-21)#


  • Backwards-incompatible: Support Falcon 2.0. Drop support for Falcon 1.x (#459). Thanks @dodumosu and @Nateyo for the PR.

6.0.0b2 (2020-01-07)#

Other changes:

  • Backwards-incompatible: Drop support for Python 2 (#440). Thanks @hugovk for the PR.

6.0.0b1 (2020-01-06)#


  • Backwards-incompatible: Schemas will now load all data from a location, not only data specified by fields. As a result, schemas with validators which examine the full input data may change in behavior. The unknown parameter on schemas may be used to alter this. For example, unknown=marshmallow.EXCLUDE will produce a behavior similar to webargs v5.

Bug fixes:

  • Backwards-incompatible: All parsers now require the Content-Type to be set correctly when processing JSON request bodies. This impacts DjangoParser, FalconParser, FlaskParser, and PyramidParser


  • Backwards-incompatible: Schema fields may not specify a location any longer, and Parser.use_args and Parser.use_kwargs now accept location (singular) instead of locations (plural). Instead of using a single field or schema with multiple locations, users are recommended to make multiple calls to use_args or use_kwargs with a distinct schema per location. For example, code should be rewritten like this:

# webargs 5.x and older
        "q1": ma.fields.Int(location="query"),
        "q2": ma.fields.Int(location="query"),
        "h1": ma.fields.Int(location="headers"),
    locations=("query", "headers"),
def foo(q1, q2, h1):

# webargs 6.x
@parser.use_args({"q1": ma.fields.Int(), "q2": ma.fields.Int()}, location="query")
@parser.use_args({"h1": ma.fields.Int()}, location="headers")
def foo(q1, q2, h1):
  • The location_handler decorator has been removed and replaced with location_loader. location_loader serves the same purpose (letting you write custom hooks for loading data) but its expected method signature is different. See the docs on location_loader for proper usage.

Thanks @sirosen for the PR!

5.5.3 (2020-01-28)#

Bug fixes:

  • CVE-2020-7965: Don’t attempt to parse JSON if request’s content type is mismatched.

5.5.2 (2019-10-06)#

Bug fixes:

  • Handle UnicodeDecodeError when parsing JSON payloads (#427). Thanks @lindycoder for the catch and patch.

5.5.1 (2019-09-15)#

Bug fixes:

  • Remove usage of deprecated when using marshmallow 3.

5.5.0 (2019-09-07)#



  • Don’t mutate globals() in webargs.fields (#411).

  • Use marshmallow 3’s Schema.from_dict if available (#415).

5.4.0 (2019-07-23)#


  • Use explicit type check for fields.DelimitedList when deciding to parse value with getlist() (#406 (comment) ).


  • Add “Parsing Lists in Query Strings” section to docs (#406).

5.3.2 (2019-06-19)#

Bug fixes:

  • marshmallow 3.0.0rc7 compatibility (#395).

5.3.1 (2019-05-05)#

Bug fixes:

  • marshmallow 3.0.0rc6 compatibility (#384).

5.3.0 (2019-04-08)#


  • Add "path" location to AIOHTTPParser, FlaskParser, and PyramidParser (#379). Thanks @zhenhua32 for the PR.

  • Add webargs.__version_info__.

5.2.0 (2019-03-16)#


  • Make the schema class used when generating a schema from a dict overridable (#375). Thanks @ThiefMaster.

5.1.3 (2019-03-11)#

Bug fixes:

5.1.2 (2019-02-03)#

Bug fixes:

  • Remove lingering usages of ValidationError.status_code (#365). Thanks @decaz for reporting.

  • Avoid AttributeError on Python<3.5.4 (#366).

  • Fix incorrect type annotations for error_headers.

  • Fix outdated docs (#367). Thanks @alexandersoto for reporting.

5.1.1.post0 (2019-01-30)#

  • Include LICENSE in sdist (#364).

5.1.1 (2019-01-28)#

Bug fixes:

  • Fix installing simplejson on Python 2 by distributing a Python 2-only wheel (#363).

5.1.0 (2019-01-11)#


  • Error handlers for AsyncParser classes may be coroutine functions.

  • Add type annotations to AsyncParser and AIOHTTPParser.

Bug fixes:

  • Fix compatibility with Flask<1.0 (#355). Thanks @hoatle for reporting.

  • Address warning on Python 3.7 about importing from

5.0.0 (2019-01-03)#


  • Backwards-incompatible: A 400 HTTPError is raised when an invalid JSON payload is passed. (#329). Thanks @zedrdave for reporting.

Other changes:

  • Backwards-incompatible: webargs.argmap2schema is removed. Use webargs.dict2schema instead.

  • Backwards-incompatible: webargs.ValidationError is removed. Use marshmallow.ValidationError instead.

# <5.0.0
from webargs import ValidationError

def auth_validator(value):
    # ...
    raise ValidationError("Authentication failed", status_code=401)

@use_args({"auth": fields.Field(validate=auth_validator)})
def auth_view(args):
    return jsonify(args)

# >=5.0.0
from marshmallow import ValidationError

def auth_validator(value):
    # ...
    raise ValidationError("Authentication failed")

@use_args({"auth": fields.Field(validate=auth_validator)}, error_status_code=401)
def auth_view(args):
    return jsonify(args)
  • Backwards-incompatible: Missing arguments will no longer be filled in when using @use_kwargs (#342, #307, #252). Use **kwargs to account for non-required fields.

# <5.0.0
    {"first_name": fields.Str(required=True), "last_name": fields.Str(required=False)}
def myview(first_name, last_name):
    # last_name is webargs.missing if it's missing from the request
    return {"first_name": first_name}

# >=5.0.0
    {"first_name": fields.Str(required=True), "last_name": fields.Str(required=False)}
def myview(first_name, **kwargs):
    # last_name will not be in kwargs if it's missing from the request
    return {"first_name": first_name}
  • simplejson is now a required dependency on Python 2 (#334). This ensures consistency of behavior across Python 2 and 3.

4.4.1 (2018-01-03)#

Bug fixes:

  • Remove usages of argmap2schema from fields.Nested, AsyncParser, and PyramidParser.

4.4.0 (2019-01-03)#

  • Deprecation: argmap2schema is deprecated in favor of dict2schema (#352).

4.3.1 (2018-12-31)#

  • Add force_all param to PyramidParser.use_args.

  • Add warning about missing arguments to AsyncParser.

4.3.0 (2018-12-30)#

  • Deprecation: Add warning about missing arguments getting added to parsed arguments dictionary (#342). This behavior will be removed in version 5.0.0.

4.2.0 (2018-12-27)#


  • Add force_all argument to use_args and use_kwargs (#252, #307). Thanks @piroux for reporting.

  • Deprecation: The status_code and headers arguments to ValidationError are deprecated. Pass error_status_code and error_headers to Parser.parse, Parser.use_args, and Parser.use_kwargs instead. (#327, #336).

  • Custom error handlers receive error_status_code and error_headers arguments. (#327).

# <4.2.0
def handle_error(error, req, schema):
    raise CustomError(error.messages)

class MyParser(FlaskParser):
    def handle_error(self, error, req, schema):
        # ...
        raise CustomError(error.messages)

# >=4.2.0
def handle_error(error, req, schema, status_code, headers):
    raise CustomError(error.messages)

# OR

def handle_error(error, **kwargs):
    raise CustomError(error.messages)

class MyParser(FlaskParser):
    def handle_error(self, error, req, schema, status_code, headers):
        # ...
        raise CustomError(error.messages)

    # OR

    def handle_error(self, error, req, **kwargs):
        # ...
        raise CustomError(error.messages)

Legacy error handlers will be supported until version 5.0.0.

4.1.3 (2018-12-02)#

Bug fixes:

  • Fix bug in AIOHTTParser that prevented calling use_args on the same view function multiple times (#273). Thanks to @dnp1 for reporting and @jangelo for the fix.

  • Fix compatibility with marshmallow 3.0.0rc1 (#330).

4.1.2 (2018-11-03)#

Bug fixes:

  • Fix serialization behavior of DelimitedList (#319). Thanks @lee3164 for the PR.

Other changes:

  • Test against Python 3.7.

4.1.1 (2018-10-25)#

Bug fixes:

  • Fix bug in AIOHTTPParser that caused a JSONDecode error when parsing empty payloads (#229). Thanks @explosic4 for reporting and thanks user @kochab for the PR.

4.1.0 (2018-09-17)#


  • Add webargs.testing module, which exposes CommonTestCase to third-party parser libraries (see comments in #287).

4.0.0 (2018-07-15)#


  • Backwards-incompatible: Custom error handlers receive the marshmallow.Schema instance as the third argument. Update any functions decorated with Parser.error_handler to take a schema argument, like so:

# 3.x
def handle_error(error, req):
    raise CustomError(error.messages)

# 4.x
def handle_error(error, req, schema):
    raise CustomError(error.messages)

See marshmallow-code/marshmallow#840 (comment) for more information about this change.

Bug fixes:

  • Backwards-incompatible: Rename webargs.async to webargs.asyncparser to fix compatibility with Python 3.7 (#240). Thanks @Reskov for the catch and patch.

Other changes:

  • Backwards-incompatible: Drop support for Python 3.4 (#243). Python 2.7 and >=3.5 are supported.

  • Backwards-incompatible: Drop support for marshmallow<2.15.0. marshmallow>=2.15.0 and >=3.0.0b12 are officially supported.

  • Use black with pre-commit for code formatting (#244).

3.0.2 (2018-07-05)#

Bug fixes:

  • Fix compatibility with marshmallow 3.0.0b12 (#242). Thanks @lafrech.

3.0.1 (2018-06-06)#

Bug fixes:

  • Respect Parser.DEFAULT_VALIDATION_STATUS when a status_code is not explicitly passed to ValidationError (#180). Thanks @foresmac for finding this.


  • Add “Returning HTTP 400 Responses” section to docs (#180).

3.0.0 (2018-05-06)#


  • Backwards-incompatible: Custom error handlers receive the request object as the second argument. Update any functions decorated with Parser.error_handler to take a req argument, like so:

# 2.x
def handle_error(error):
    raise CustomError(error.messages)

# 3.x
def handle_error(error, req):
    raise CustomError(error.messages)
  • Backwards-incompatible: Remove unused instance and kwargs arguments of argmap2schema.

  • Backwards-incompatible: Remove Parser.load method (Parser now calls Schema.load directly).

These changes shouldn’t affect most users. However, they might break custom parsers calling these methods. (#222)

  • Drop support for aiohttp<3.0.0.

2.1.0 (2018-04-01)#


  • Respect data_key field argument (in marshmallow 3). Thanks @lafrech.

2.0.0 (2018-02-08)#


  • Drop support for aiohttp<2.0.0.

  • Remove use of deprecated Request.has_body attribute in aiohttpparser (#186). Thanks @ariddell for reporting.

1.10.0 (2018-02-08)#


  • Add support for marshmallow>=3.0.0b7 (#188). Thanks @lafrech.


  • Support for aiohttp<2.0.0 is deprecated and will be removed in webargs 2.0.0.

1.9.0 (2018-02-03)#



  • Fix examples in examples/ directory.

1.8.1 (2017-07-17)#

Bug fixes:

  • Fix behavior of AIOHTTPParser.use_args when as_kwargs=True is passed with a Schema (#179). Thanks @Itayazolay.

1.8.0 (2017-07-16)#


  • AIOHTTPParser supports class-based views, i.e. aiohttp.web.View (#177). Thanks @daniel98321.

1.7.0 (2017-06-03)#


  • AIOHTTPParser.use_args and AIOHTTPParser.use_kwargs work with async def coroutines (#170). Thanks @zaro.

1.6.3 (2017-05-18)#


  • Fix Flask error handling docs in “Framework support” section (#168). Thanks @nebularazer.

1.6.2 (2017-05-16)#

Bug fixes:

  • Fix parsing multiple arguments in AIOHTTParser (#165). Thanks @ariddell for reporting and thanks @zaro for reporting.

1.6.1 (2017-04-30)#

Bug fixes:

  • Fix form parsing in aiohttp>=2.0.0. Thanks @DmitriyS for the PR.

1.6.0 (2017-03-14)#

Bug fixes:

  • Fix compatibility with marshmallow 3.x.

Other changes:

  • Drop support for Python 2.6 and 3.3.

  • Support marshmallow>=2.7.0.

1.5.3 (2017-02-04)#

Bug fixes:

  • Port fix from release 1.5.2 to AsyncParser. This fixes #146 for AIOHTTPParser.

  • Handle invalid types passed to DelimitedList (#149). Thanks @psconnect-dev for reporting.

1.5.2 (2017-01-08)#

Bug fixes:

  • Don’t add marshmallow.missing to original_data when using marshmallow.validates_schema(pass_original=True) (#146). Thanks @lafrech for reporting and for the fix.

Other changes:

  • Test against Python 3.6.

1.5.1 (2016-11-27)#

Bug fixes:

  • Fix handling missing nested args when many=True (#120, #145). Thanks @chavz and @Bangertm for reporting.

  • Fix behavior of load_from in AIOHTTPParser.

1.5.0 (2016-11-22)#


  • The use_args and use_kwargs decorators add a reference to the undecorated function via the __wrapped__ attribute. This is useful for unit-testing purposes (#144). Thanks @EFF for the PR.

Bug fixes:

  • If load_from is specified on a field, first check the field name before checking load_from (#118). Thanks @jasonab for reporting.

1.4.0 (2016-09-29)#

Bug fixes:

  • Prevent error when rendering validation errors to JSON in Flask (e.g. when using Flask-RESTful) (#122). Thanks @frol for the catch and patch. NOTE: Though this is a bugfix, this is a potentially breaking change for code that needs to access the original ValidationError object.

# Before
def handle_validation_error(err):
    return jsonify({"errors": err.messages}), 422

# After
def handle_validation_error(err):
    # The marshmallow.ValidationError is available on err.exc
    return jsonify({"errors": err.exc.messages}), 422

1.3.4 (2016-06-11)#

Bug fixes:

  • Fix bug in parsing form in Falcon>=1.0.

1.3.3 (2016-05-29)#

Bug fixes:

  • Fix behavior for nullable List fields (#107). Thanks @shaicantor for reporting.

1.3.2 (2016-04-14)#

Bug fixes:

  • Fix passing a schema factory to use_kwargs (#103). Thanks @ksesong for reporting.

1.3.1 (2016-04-13)#

Bug fixes:

  • Fix memory leak when calling parser.parse with a dict in a view (#101). Thanks @frankslaughter for reporting.

  • aiohttpparser: Fix bug in handling bulk-type arguments.


  • Massive refactor of tests (#98).

  • Docs: Fix incorrect use_args example in Tornado section (#100). Thanks @frankslaughter for reporting.

  • Docs: Add “Mixing Locations” section (#90). Thanks @tuukkamustonen.

1.3.0 (2016-04-05)#


  • Add bulk-type arguments support for JSON parsing by passing many=True to a Schema (#81). Thanks @frol.

Bug fixes:

  • Fix JSON parsing in Flask<=0.9.0. Thanks @brettdh for the PR.

  • Fix behavior of status_code argument to ValidationError (#85). This requires marshmallow>=2.7.0. Thanks @ParthGandhi for reporting.


  • Docs: Add “Custom Fields” section with example of using a Function field (#94). Thanks @brettdh for the suggestion.

1.2.0 (2016-01-04)#


  • Add view_args request location to FlaskParser (#82). Thanks @oreza for the suggestion.

Bug fixes:

  • Use the value of load_from as the key for error messages when it is provided (#83). Thanks @immerrr for the catch and patch.

1.1.1 (2015-11-14)#

Bug fixes:

  • aiohttpparser: Fix bug that raised a JSONDecodeError raised when parsing non-JSON requests using default locations (#80). Thanks @leonidumanskiy for reporting.

  • Fix parsing JSON requests that have a vendor media type, e.g. application/vnd.api+json.

1.1.0 (2015-11-08)#


  • Parser.parse, Parser.use_args and Parser.use_kwargs can take a Schema factory as the first argument (#73). Thanks @DamianHeard for the suggestion and the PR.


  • Docs: Add “Custom Parsers” section with example of parsing nested querystring arguments (#74). Thanks @dwieeb.

  • Docs: Add “Advanced Usage” page.

1.0.0 (2015-10-19)#


  • Add AIOHTTPParser (#71).

  • Add webargs.async module with AsyncParser.

Bug fixes:

  • If an empty list is passed to a List argument, it will be parsed as an empty list rather than being excluded from the parsed arguments dict (#70). Thanks @mTatcher for catching this.

Other changes:

  • Backwards-incompatible: When decorating resource methods with FalconParser.use_args, the parsed arguments dictionary will be positioned after the request and response arguments.

  • Backwards-incompatible: When decorating views with DjangoParser.use_args, the parsed arguments dictionary will be positioned after the request argument.

  • Backwards-incompatible: Parser.get_request_from_view_args gets passed a view function as its first argument.

  • Backwards-incompatible: Remove logging from default error handlers.

0.18.0 (2015-10-04)#


  • Add FalconParser (#63).

  • Add fields.DelimitedList (#66). Thanks @jmcarp.

  • TornadoParser will parse json with simplejson if it is installed.

  • BottleParser caches parsed json per-request for improved performance.

No breaking changes. Yay!

0.17.0 (2015-09-29)#


  • TornadoParser returns unicode strings rather than bytestrings (#41). Thanks @thomasboyt for the suggestion.

  • Add Parser.get_default_request and Parser.get_request_from_view_args hooks to simplify Parser implementations.

  • Backwards-compatible: webargs.core.get_value takes a Field as its last argument. Note: this is technically a breaking change, but this won’t affect most users since get_value is only used internally by Parser classes.


  • Add examples/ (demonstrates using Python 3 function annotations to define request arguments).

  • Fix examples. Thanks @hyunchel for catching an error in the Flask error handling docs.

Bug fixes:

  • Correctly pass validate and force_all params to PyramidParser.use_args.

0.16.0 (2015-09-27)#

The major change in this release is that webargs now depends on marshmallow for defining arguments and validation.

Your code will need to be updated to use Fields rather than Args.

# Old API
from webargs import Arg

args = {
    "name": Arg(str, required=True),
    "password": Arg(str, validate=lambda p: len(p) >= 6),
    "display_per_page": Arg(int, default=10),
    "nickname": Arg(multiple=True),
    "Content-Type": Arg(dest="content_type", location="headers"),
    "location": Arg({"city": Arg(str), "state": Arg(str)}),
    "meta": Arg(dict),

# New API
from webargs import fields

args = {
    "name": fields.Str(required=True),
    "password": fields.Str(validate=lambda p: len(p) >= 6),
    "display_per_page": fields.Int(load_default=10),
    "nickname": fields.List(fields.Str()),
    "content_type": fields.Str(load_from="Content-Type"),
    "location": fields.Nested({"city": fields.Str(), "state": fields.Str()}),
    "meta": fields.Dict(),


  • Error messages for all arguments are “bundled” (#58).


  • Backwards-incompatible: Replace Args with marshmallow fields (#61).

  • Backwards-incompatible: When using use_kwargs, missing arguments will have the special value missing rather than None.

  • TornadoParser raises a custom HTTPError with a messages attribute when validation fails.

Bug fixes:

  • Fix required validation of nested arguments (#39, #51). These are fixed by virtue of using marshmallow’s Nested field. Thanks @ewang and @chavz for reporting.


  • Updated docs.

  • Add examples/

  • Tested against Python 3.5.

0.15.0 (2015-08-22)#


  • If a parsed argument is None, the type conversion function is not called #54. Thanks @marcellarius.

Bug fixes:

  • Fix parsing nested Args when the argument is missing from the input (#52). Thanks @stas.

0.14.0 (2015-06-28)#


  • Add parsing of matchdict to PyramidParser. Thanks @hartror.

Bug fixes:

  • Fix PyramidParser's use_kwargs method (#42). Thanks @hartror for the catch and patch.

  • Correctly use locations passed to Parser’s constructor when using use_args (#44). Thanks @jacebrowning for the catch and patch.

  • Fix behavior of default and dest argument on nested Args (#40 and #46). Thanks @stas.


  • A 422 response is returned to the client when a ValidationError is raised by a parser (#38).

0.13.0 (2015-04-05)#


  • Support for webapp2 via the webargs.webapp2parser module. Thanks @Trii.

  • Store argument name on RequiredArgMissingError. Thanks @stas.

  • Allow error messages for required validation to be overriden. Thanks again @stas.


  • Remove source parameter from Arg.

0.12.0 (2015-03-22)#


  • Store argument name on ValidationError (#32). Thanks @alexmic for the suggestion. Thanks @stas for the patch.

  • Allow nesting of dict subtypes.

0.11.0 (2015-03-01)#


  • Add dest parameter to Arg constructor which determines the key to be added to the parsed arguments dictionary (#32).

  • Backwards-incompatible: Rename targets parameter to locations in Parser constructor, Parser#parse_arg, Parser#parse, Parser#use_args, and Parser#use_kwargs.

  • Backwards-incompatible: Rename Parser#target_handler to Parser#location_handler.


  • The source parameter is deprecated in favor of the dest parameter.

Bug fixes:

  • Fix validate parameter of DjangoParser#use_args.

0.10.0 (2014-12-23)#

  • When parsing a nested Arg, filter out extra arguments that are not part of the Arg's nested dict (#28). Thanks Derrick Gilland for the suggestion.

  • Fix bug in parsing Args with both type coercion and multiple=True (#30). Thanks Steven Manuatu for reporting.

  • Raise RequiredArgMissingError when a required argument is missing on a request.

0.9.1 (2014-12-11)#

  • Fix behavior of multiple=True when nesting Args (#29). Thanks Derrick Gilland for reporting.

0.9.0 (2014-12-08)#

  • Pyramid support thanks to @philtay.

  • User-friendly error messages when Arg type conversion/validation fails. Thanks Andriy Yurchuk.

  • Allow use argument to be a list of functions.

  • Allow Args to be nested within each other, e.g. for nested dict validation. Thanks @saritasa for the suggestion.

  • Backwards-incompatible: Parser will only pass ValidationErrors to its error handler function, rather than catching all generic Exceptions.

  • Backwards-incompatible: Rename Parser.TARGET_MAP to Parser.__target_map__.

  • Add a short-lived cache to the Parser class that can be used to store processed request data for reuse.

  • Docs: Add example usage with Flask-RESTful.

0.8.1 (2014-10-28)#

  • Fix bug in TornadoParser that raised an error when request body is not a string (e.g when it is a Future). Thanks Josh Carp.

0.8.0 (2014-10-26)#

  • Fix Parser.use_kwargs behavior when an Arg is allowed missing. The allow_missing attribute is ignored when use_kwargs is called.

  • default may be a callable.

  • Allow ValidationError to specify a HTTP status code for the error response.

  • Improved error logging.

  • Add 'query' as a valid target name.

  • Allow a list of validators to be passed to an Arg or Parser.parse.

  • A more useful __repr__ for Arg.

  • Add examples and updated docs.

0.7.0 (2014-10-18)#

  • Add source parameter to Arg constructor. Allows renaming of keys in the parsed arguments dictionary. Thanks Josh Carp.

  • FlaskParser's handle_error method attaches the string representation of validation errors on['message']. The raised exception is stored on['exc'].

  • Additional keyword arguments passed to Arg are stored as metadata.

0.6.2 (2014-10-05)#

  • Fix bug in TornadoParser's handle_error method. Thanks Josh Carp.

  • Add error parameter to Parser constructor that allows a custom error message to be used if schema-level validation fails.

  • Fix bug that raised a UnicodeEncodeError on Python 2 when an Arg’s validator function received non-ASCII input.

0.6.1 (2014-09-28)#

  • Fix regression with parsing an Arg with both default and target set (see issue #11).

0.6.0 (2014-09-23)#

  • Add validate parameter to Parser.parse and Parser.use_args. Allows validation of the full parsed output.

  • If allow_missing is True on an Arg for which None is explicitly passed, the value will still be present in the parsed arguments dictionary.

  • Backwards-incompatible: Parser's parse_* methods return webargs.core.Missing if the value cannot be found on the request. NOTE: webargs.core.Missing will not show up in the final output of Parser.parse.

  • Fix bug with parsing empty request bodies with TornadoParser.

0.5.1 (2014-08-30)#

  • Fix behavior of Arg's allow_missing parameter when multiple=True.

  • Fix bug in tornadoparser that caused parsing JSON arguments to fail.

0.5.0 (2014-07-27)#

  • Fix JSON parsing in Flask parser when Content-Type header contains more than just application/json. Thanks Samir Uppaluru for reporting.

  • Backwards-incompatible: The use parameter to Arg is called before type conversion occurs. Thanks Eric Wang for the suggestion.

  • Tested on Tornado>=4.0.

0.4.0 (2014-05-04)#

  • Custom target handlers can be defined using the Parser.target_handler decorator.

  • Error handler can be specified using the Parser.error_handler decorator.

  • Args can define their request target by passing in a target argument.

  • Backwards-incompatible: DEFAULT_TARGETS is now a class member of Parser. This allows subclasses to override it.

0.3.4 (2014-04-27)#

  • Fix bug that caused use_args to fail on class-based views in Flask.

  • Add allow_missing parameter to Arg.

0.3.3 (2014-03-20)#

  • Awesome contributions from the open-source community!

  • Add use_kwargs decorator. Thanks @venuatu.

  • Tornado support thanks to @jvrsantacruz.

  • Tested on Python 3.4.

0.3.2 (2014-03-04)#

  • Fix bug with parsing JSON in Flask and Bottle.

0.3.1 (2014-03-03)#

  • Remove print statements in Oops.

0.3.0 (2014-03-02)#

  • Add support for repeated parameters (#1).

  • Backwards-incompatible: All parse_* methods take arg as their fourth argument.

  • Add error_handler param to Parser.

0.2.0 (2014-02-26)#

  • Bottle support.

  • Add targets param to Parser. Allows setting default targets.

  • Add files target.

0.1.0 (2014-02-16)#

  • First release.

  • Parses JSON, querystring, forms, headers, and cookies.

  • Support for Flask and Django.