multipartDataRequestFilter Filter

Select requests carrying a multipart/form-data body, the standard wire format for browser file uploads and rich form posts.

multipartDataRequestFilter is the dedicated selector for file uploads and other multipart submissions in a Fluxzy rule. It reads the request Content-Type header and matches every request that carries a multipart/form-data body. Use it whenever you want to debug, throttle or audit the upload side of your application.

When to use this filter

Reach for multipartDataRequestFilter when a rule should only apply to requests carrying a multipart/form-data body. This is the wire format used by browsers for file uploads, by curl with -F, and by HTTP clients sending rich forms.

Typical situations:

Throttling uploads to a specific endpoint to reproduce slow network conditions.
Tagging every multipart submission for review in the capture view.
Rejecting oversized uploads on a test environment without involving the back end.

The filter evaluates on the requestHeaderReceivedFromClient scope, so the Content-Type header is already parsed when it fires. Combine it with pathFilter to scope to a specific upload endpoint.

Real world examples

Throttle file uploads to a specific endpoint

Slow down every multipart upload heading to /api/uploads to reproduce a customer report about timeouts on weak connections.

rules:
- filter:
    typeKind: FilterCollection
    children:
    - typeKind: MultipartDataRequestFilter
    - typeKind: PathFilter
      pattern: /api/uploads
      operation: StartsWith
  actions:
  - typeKind: AverageThrottleAction
    bandwidthBytesPerSeconds: 16384

Tag every multipart submission

Apply a tag to all file upload requests so they group together in the Fluxzy capture view, making it easier to audit user submissions.

rules:
- filter:
    typeKind: MultipartDataRequestFilter
  actions:
  - typeKind: ApplyTagAction
    tag:
      value: file-upload

Reject multipart uploads on a closed endpoint

Return a canned 413 response for every multipart submission to a path that should no longer accept uploads, useful when sunsetting an upload feature.

rules:
- filter:
    typeKind: FilterCollection
    children:
    - typeKind: MultipartDataRequestFilter
    - typeKind: PathFilter
      pattern: /legacy/upload
      operation: StartsWith
  actions:
  - typeKind: RejectWithStatusCodeAction
    statusCode: 413

Reference

multipartDataRequestFilter

Description

Select request sending 'multipart/form-data' body. Filtering is made by inspecting value of Content-Type header

Evaluation scope

Evaluation scope defines the timing where this filter will be applied.

requestHeaderReceivedFromClient This scope occurs the moment fluxzy parsed the request header receiveid from client

YAML configuration name

multipartDataRequestFilter

Settings

This filter has no specific characteristic

The following table describes the customizable properties available for this filter:

Property	Type	Description	DefaultValue
inverted	boolean	Negate the filter result	false

Example of usage

The following examples apply a comment to the filtered exchange

Select exchanges having request header dnt: 1.

rules:
- filter:
    typeKind: RequestHeaderFilter
    headerName: dnt
    pattern: 1
    operation: Exact
  actions:
  - typeKind: ApplyCommentAction
    comment: filter was applied

Select exchanges issued by Chrome 112 by checking User-Agent.

rules:
- filter:
    typeKind: RequestHeaderFilter
    headerName: User-Agent
    pattern: 'Chrome/112 '
    operation: Contains
  actions:
  - typeKind: ApplyCommentAction
    comment: filter was applied

.NET reference

View definition of MultipartDataRequestFilter for .NET integration.

Frequently asked questions

How does the filter recognize a multipart request?

It inspects the request Content-Type header. Any value starting with multipart/form-data matches, including those carrying the boundary parameter like multipart/form-data; boundary=----WebKitFormBoundary...

Does it parse the form parts?

No. multipartDataRequestFilter only checks the Content-Type header, it does not decode the body. Use a custom .NET filter if you need to inspect individual parts or file names.

Is multipart used for anything besides file uploads?

Yes. Any form with a file input, but also forms that mix text fields with binary data, use multipart/form-data. SOAP attachments and some webhook payloads also rely on multipart.

What is the difference with formUrlEncodedRequestFilter?

multipartDataRequestFilter matches application/multipart/form-data, used when a request includes files or binary data. formUrlEncodedRequestFilter matches application/x-www-form-urlencoded, used for plain text form fields only.

Learn more about Fluxzy rules

Rule file syntax reference Importing YAML rules into Fluxzy Desktop Using rule files with Fluxzy CLI

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