Fiddler

Fiddler by Telerik (Progress Software) is a family of HTTP debugging proxy tools for capturing, inspecting, modifying, and replaying HTTP and HTTPS traffic between a machine and the internet. The line comprises Fiddler Everywhere (the cross-platform flagship), Fiddler Classic (the original Windows proxy, licensed for non-commercial use only as of 2026-08-03), Fiddler Everywhere Reporter (a free capture-and-report companion) and FiddlerCore (an embeddable proxy engine for .NET). Fiddler publishes no hosted REST API; its programmatic surface is a first-party Model Context Protocol server hosted by the Fiddler Everywhere desktop app on the loopback interface, exposing 20 documented tools that let a coding agent start captures, read sessions and request/response details, apply filters, create traffic-rewriting rules, run a reverse proxy and cache LLM agent calls. Progress also publishes three official Agent Skills for it. Fiddler Jam was retired by Progress on 2024-07-01.

Fiddler publishes 5 APIs on the APIs.io network. Tagged areas include API Debugging, HTTP Debugging, HTTP Proxy, Performance Testing, and Traffic Inspection.

Fiddler’s developer surface includes documentation, API reference, getting-started guide, support, engineering blog, pricing, signup flow, and 31 more developer resources.

🌐 Visit website 📡 Source on GitHub

47.1/100 developing ▬ flat Agent 20/100 agent aware saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

AccessFreemium

5 APIs 1 MCP Servers

API Debugging HTTP Debugging HTTP Proxy Performance TestingTraffic InspectionWeb Development Developer Tools MCP Agent Tooling

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 47.1/100 · developing

Contract Quality 0.0 / 25

Developer Ergonomics 12.4 / 20

Access Clarity 20.0 / 20

Operational Transparency 7.5 / 13

Contract Governance 0.0 / 12

Discoverability 7.2 / 10

Agent readiness — 20/100 · agent aware

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/fiddler: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 5

Individual APIs this provider publishes, each with its own machine-readable definition.

Fiddler Everywhere

Fiddler Everywhere is a cross-platform web debugging proxy for macOS, Windows, and Linux. It captures HTTP and HTTPS traffic, provides API composition capabilities, and includes...

Fiddler Everywhere MCP Server

The Fiddler Everywhere MCP server is the only programmatic interface Progress Telerik publishes for Fiddler. It is hosted by the desktop application on the loopback interface at...

Fiddler Classic

Fiddler Classic is the original free Windows-based HTTP debugging proxy for logging all HTTP and HTTPS traffic between a computer and the Internet. It supports traffic inspectio...

FiddlerCore

FiddlerCore is the embeddable Fiddler proxy engine for .NET and .NET Standard applications, licensed and delivered as a download rather than through a public package registry. T...

Fiddler Jam

RETIRED. Fiddler Jam was a browser-based troubleshooting solution that let non-technical users capture HTTP traffic logs and share them with development teams. Progress Software...

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

Fiddler Everywhere MCP Server

Fiddler Everywhere ships a first-party Model Context Protocol server that lets a coding agent drive the locally installed proxy: start browser/terminal/ network captures, read c...

MCP SERVER

Pricing Plans 1

Published pricing tiers and plan structures.

Fiddler Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Fiddler Rate Limits

0 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Fiddler Finops

FINOPS

Security Posture 4

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Fiddler Authentication

3 schemes

SECURITY

Fiddler Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Fiddler Vulnerability Disclosure

Bugcrowd · security.txt · contact published

SECURITY

Fiddler Trust Center

ISO/IEC 27001, SOC 2, HIPAA

SECURITY

Resources

Get Started 3

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

SignUp

SignUp

Login

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

MCPServer

AgentSkill

LLMsTxt

WellKnown

Design & Contract 3

Pagination, idempotency, versioning, errors, and events

Conventions

Conventions

Conformance

Conformance

Lifecycle

Lifecycle

Build 3

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Packages

Packages

SDKs

SDKs

Access & Security 7

Authentication, authorization, and security posture

Authentication

Compliance

SecurityTxt

Security

VulnerabilityDisclosure

VulnerabilityDisclosure

TrustCenter

TrustCenter

DomainSecurity

DomainSecurity

Scroll for all 7

Learn 1

Tutorials, courses, talks, and written guidance

Videos

Videos

Operate 6

Status, limits, changes, and where to get help

Support

Roadmap

RateLimits

ChangeLog

StatusPage

Deprecation

Commercial 4

Pricing, plans, and the legal terms of use

Pricing

Plans

TermsOfService

PrivacyPolicy

Company 4

The organization behind the API

Website

Website

Blog

Blog

LinkedIn

Twitter

Twitter

Other 1

Properties that don't map to a standard resource type

Download

Download

Source (apis.yml)

aid: fiddler
name: Fiddler
description: Fiddler by Telerik (Progress Software) is a family of HTTP debugging proxy tools for capturing, inspecting, modifying,
  and replaying HTTP and HTTPS traffic between a machine and the internet. The line comprises Fiddler Everywhere (the cross-platform
  flagship), Fiddler Classic (the original Windows proxy, licensed for non-commercial use only as of 2026-08-03), Fiddler
  Everywhere Reporter (a free capture-and-report companion) and FiddlerCore (an embeddable proxy engine for .NET). Fiddler
  publishes no hosted REST API; its programmatic surface is a first-party Model Context Protocol server hosted by the Fiddler
  Everywhere desktop app on the loopback interface, exposing 20 documented tools that let a coding agent start captures, read
  sessions and request/response details, apply filters, create traffic-rewriting rules, run a reverse proxy and cache LLM
  agent calls. Progress also publishes three official Agent Skills for it. Fiddler Jam was retired by Progress on 2024-07-01.
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/fiddler.png
tags:
- API Debugging
- HTTP Debugging
- HTTP Proxy
- Performance Testing
- Traffic Inspection
- Web Development
- Developer Tools
- MCP
- Agent Tooling
tags_raw:
- API Debugging
- HTTP Debugging
- HTTP Proxy
- Performance Testing
- Traffic Inspection
- Web Development
- Developer Tools
- Model Context Protocol
- Agent Tooling
url: https://raw.githubusercontent.com/api-evangelist/fiddler/refs/heads/main/apis.yml
created: '2026-03-26'
modified: '2026-08-29'
specificationVersion: '0.23'
apis:
- aid: fiddler:fiddler-everywhere
  name: Fiddler Everywhere
  description: Fiddler Everywhere is a cross-platform web debugging proxy for macOS, Windows, and Linux. It captures HTTP
    and HTTPS traffic, provides API composition capabilities, and includes collaboration features for team debugging and API
    testing workflows.
  humanURL: https://www.telerik.com/fiddler/fiddler-everywhere
  tags:
  - API Testing
  - Cross-Platform
  - HTTP Debugging
  - Traffic Capture
  tags_raw:
  - API Testing
  - Cross Platform
  - HTTP Debugging
  - Traffic Capture
  properties:
  - type: Documentation
    url: https://docs.telerik.com/fiddler-everywhere/introduction
  - type: GettingStarted
    url: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/installation-and-setup/quickstart-windows
  - type: Download
    url: https://www.telerik.com/download/fiddler-everywhere
- aid: fiddler:fiddler-everywhere-mcp
  name: Fiddler Everywhere MCP Server
  description: 'The Fiddler Everywhere MCP server is the only programmatic interface Progress Telerik publishes for Fiddler.
    It is hosted by the desktop application on the loopback interface at http://localhost:8868/mcp over streamable HTTP, authenticated
    with an API key generated in Settings > MCP Server, and gated to the Pro and Enterprise tiers. It exposes 20 documented
    tools covering status and login, browser/terminal/network capture, session retrieval and filtering, traffic-rewriting
    rules, reverse-proxy configuration and LLM agent-call caching. Because the endpoint is loopback-bound it is not reachable
    by a remote agent: a person must install, license and sign in to Fiddler Everywhere first.'
  humanURL: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/agent-tools/fiddler-mcp-server
  baseURL: http://localhost:8868/mcp
  baseURL_note: Recorded as loopback deliberately. This is the real, provider-documented base for the server; there is no
    hosted host to substitute, and putting a telerik.com host here would name an endpoint that does not exist.
  tags:
  - MCP
  - Agent Tooling
  - HTTP Debugging
  - Traffic Capture
  tags_raw:
  - Model Context Protocol
  - Agent Tooling
  - HTTP Debugging
  - Traffic Capture
  properties:
  - type: MCPServer
    url: mcp/fiddler-mcp.yml
  - type: APIReference
    url: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/agent-tools/fiddler-mcp-server
  - type: AgentSkill
    url: skills/_index.yml
  - type: Authentication
    url: authentication/fiddler-authentication.yml
  - type: Conventions
    url: conventions/fiddler-conventions.yml
- aid: fiddler:fiddler-classic
  name: Fiddler Classic
  description: Fiddler Classic is the original free Windows-based HTTP debugging proxy for logging all HTTP and HTTPS traffic
    between a computer and the Internet. It supports traffic inspection, breakpoints, and extensibility through FiddlerScript
    and extensions. As of 2026-08-03 it is licensed for non-commercial use only; commercial users were given 45 days to move
    to Fiddler Everywhere, with commercial use unsupported after 2026-09-17.
  humanURL: https://www.telerik.com/fiddler/fiddler-classic
  tags:
  - Free Tool
  - HTTP Debugging
  - Traffic Logging
  - Windows
  properties:
  - type: Documentation
    url: https://docs.telerik.com/fiddler/configure-fiddler/tasks/configurefiddler
  - type: Download
    url: https://www.telerik.com/download/fiddler
  - type: Deprecation
    url: https://www.telerik.com/purchase/license-agreement/fiddler
- aid: fiddler:fiddlercore
  name: FiddlerCore
  description: FiddlerCore is the embeddable Fiddler proxy engine for .NET and .NET Standard applications, licensed and delivered
    as a download rather than through a public package registry. Two first-party helper libraries (FiddlerCore5.NetworkConnections
    and BCMakeCert) are published on NuGet by Progress, both last released 2023-03-14.
  humanURL: https://www.telerik.com/fiddlercore
  tags:
  - Embeddable Proxy
  - .NET
  - SDK
  - Traffic Capture
  properties:
  - type: Documentation
    url: https://www.telerik.com/support/fiddlercore
  - type: SDKs
    url: packages/fiddler-packages.yml
- aid: fiddler:fiddler-jam
  name: Fiddler Jam
  description: RETIRED. Fiddler Jam was a browser-based troubleshooting solution that let non-technical users capture HTTP
    traffic logs and share them with development teams. Progress Software discontinued it on 2024-07-01, closed the portal
    and deleted all recordings on 2024-12-01, and states it is "no longer a part of the Progress Software portfolio in any
    way". Its former product page and documentation both return 404; the retirement notice on the purchase page is the only
    surviving surface. Kept in this profile so the retirement is on the record rather than the product silently vanishing.
  humanURL: https://www.telerik.com/purchase/fiddler-jam
  lifecycle: retired
  retired: '2024-07-01'
  tags:
  - Browser Extension
  - Collaboration
  - Retired
  - Troubleshooting
  properties:
  - type: Deprecation
    url: https://www.telerik.com/purchase/fiddler-jam
common:
- type: Website
  url: https://www.telerik.com/fiddler
- type: Documentation
  url: https://docs.telerik.com/fiddler-everywhere/introduction
- type: APIReference
  url: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/agent-tools/fiddler-mcp-server
- type: GettingStarted
  url: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/installation-and-setup/quickstart-windows
- type: Support
  url: https://www.telerik.com/support/fiddler-everywhere
- type: Blog
  url: https://www.telerik.com/blogs/fiddler
- type: Roadmap
  url: https://feedback.telerik.com/fiddler-everywhere
- type: GitHubOrganization
  url: https://github.com/telerik
- type: Pricing
  url: https://www.telerik.com/purchase/fiddler
- type: Plans
  url: plans/fiddler-plans-pricing.yml
- type: RateLimits
  url: rate-limits/fiddler-rate-limits.yml
- type: SignUp
  url: https://www.telerik.com/login#register
- type: Login
  url: https://www.telerik.com/login
- type: TermsOfService
  url: https://www.progress.com/legal/terms-of-use
- type: PrivacyPolicy
  url: https://www.progress.com/legal/privacy-policy
- type: Download
  url: https://www.telerik.com/download/fiddler-everywhere
- type: MCPServer
  url: mcp/fiddler-mcp.yml
- type: AgentSkill
  url: skills/_index.yml
- type: LLMsTxt
  url: llms/fiddler-llms.txt
- type: Packages
  url: packages/fiddler-packages.yml
- type: SDKs
  url: packages/fiddler-packages.yml
- type: Authentication
  url: authentication/fiddler-authentication.yml
- type: Conventions
  url: conventions/fiddler-conventions.yml
- type: Conformance
  url: conformance/fiddler-conformance.yml
- type: Compliance
  url: conformance/fiddler-conformance.yml
- type: ChangeLog
  url: changelog/fiddler-changelog.yml
- type: Lifecycle
  url: lifecycle/fiddler-lifecycle.yml
- type: StatusPage
  url: https://status.telerik.com
- type: Deprecation
  url: https://www.telerik.com/purchase/license-agreement/fiddler
- type: WellKnown
  url: well-known/fiddler-well-known.yml
- type: SecurityTxt
  url: well-known/fiddler-security.txt
- type: Security
  url: security/fiddler-vulnerability-disclosure.yml
- type: VulnerabilityDisclosure
  url: security/fiddler-vulnerability-disclosure.yml
- type: TrustCenter
  url: security/fiddler-trust-center.yml
- type: DomainSecurity
  url: security/fiddler-domain-security.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/telerik
- type: Twitter
  url: https://twitter.com/telerik
- type: Videos
  url: https://www.youtube.com/c/progresssw
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-08-29'
  status: enriched
  artifacts_added: 16
  pass: local-v1
x-identity-corrections:
  date: '2026-08-29'
  note: Three pointers in this profile named a DIFFERENT COMPANY and were removed. Fiddler here is the Telerik/Progress HTTP
    debugging proxy; the removed pointers belonged to Fiddler AI (fiddler.ai), the ML observability vendor.
  removed:
  - type: GitHubOrganization
    url: https://github.com/fiddler-labs
    reason: HTTP 200 but the org page title is "Fiddler AI" — a different company. Replaced with https://github.com/telerik,
      which hosts telerik/fiddler-agent-tools, telerik/fiddler-everywhere and telerik/fiddler-everywhere-docs.
  - type: LinkedIn
    url: https://www.linkedin.com/company/fiddler-ai
    reason: HTTP 200, page title "Fiddler AI | LinkedIn" — a different company.
  - type: Twitter
    url: https://twitter.com/anthropaboroshi
    reason: HTTP 404, and the handle has no relationship to Fiddler or Telerik.
  repaired:
  - type: GettingStarted
    was: https://docs.telerik.com/fiddler-everywhere/get-started/quickstart
    now: https://www.telerik.com/fiddler/fiddler-everywhere/documentation/installation-and-setup/quickstart-windows
    reason: The former URL returned 404; the docs tree moved to installation-and-setup/.
  - aid: fiddler:fiddler-jam
    was: https://www.telerik.com/fiddler/jam
    now: https://www.telerik.com/purchase/fiddler-jam
    reason: Both the product page and docs.telerik.com/fiddler-jam/introduction returned 404 — the product was retired in
      2024. The purchase page still carries the retirement notice.

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