Pretender.js review

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Pretender.js is an open-source JavaScript mock server library for browser applications and tests. It temporarily replaces native XMLHttpRequest and Fetch, then routes requests to developer-defined handlers. The Express- and Sinatra-inspired DSL supports GET, PUT, POST, DELETE, PATCH, and HEAD routes, making it suited to frontend developers who need controlled API behavior during browser testing without adopting a hosted mock service.

Its main strength is request-level control. Routes can use static or dynamic path segments, route parameters, and query-parameter access through request objects. Handlers can return custom status codes, headers, and response bodies, with promise-based, delayed, synchronous, or manually resolved responses. Passthrough routes allow selected requests to reach the real network, while request tracking and handler call counts help inspect interaction patterns during tests.

The trade-off is a narrow browser-first scope. Pretender.js is distributed as an npm package for web use rather than as a standalone local mock server or hosted mock API service. It also does not provide an OpenAPI import workflow or generated mock-data feature. Choose it when browser request interception, route matching, and programmable responses are the priority. Teams seeking specification-driven mocks, broader platform coverage, or a separately deployed mock API should choose a tool built around those needs instead.

Pretender.js pros and cons

• Where it wins
  • Intercepts both XMLHttpRequest and Fetch requests
  • Supports dynamic routes, query parameters, and custom responses
  • Adds delays, passthroughs, request tracking, and manual resolution
• Where it doesn't
  • Browser-only focus limits use in non-browser mock environments
  • No OpenAPI import or generated mock-data workflow
  • Not a hosted mock API service or standalone local server

Pretender.js fact sheet, pricing and score →

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Last updated 7 Oct 2026 · How we research and update