HeaderCraft Dev - HTTP Header & Request Modifier

Free, local-first MV3 header modifier with auto-disable timers, environment badge, response delay simulation, and rule hit counters.

HeaderCraft Dev is a developer and QA testing tool for configuring HTTP headers, URL redirects, query parameters, API mock responses, and testing cookies directly in Chrome. It helps developers and QA engineers test applications against different request configurations, authentication states, API responses, development servers, and network conditions without changing application code. KEY FEATURES HTTP Header Modification • Add, modify, append, or remove supported request headers. • Modify supported response headers for local testing. • Configure authentication and custom headers for development and QA workflows. • Apply rules using URL and resource-type matching. URL Redirects • Redirect web resources and API endpoints to local development servers. • Test local versions of resources without changing application code. • Support exact, prefix, and regular-expression matching. Query Parameters • Add, modify, or remove URL query parameters. • Configure parameters used for development, debugging, and testing. • Remove unwanted parameters from matching requests. API Mocking • Create local mock responses for supported requests. • Test frontend behavior without modifying backend services. • Configure custom HTTP status codes and response bodies. • Simulate common API success and error scenarios. Cookie Vault • Store testing cookies by domain. • Import and manage cookies for authenticated testing workflows. • Restore testing sessions when working with supported domains. • Keep test cookie configurations organized within the extension. Workspaces and Folders • Organize testing configurations into separate workspaces. • Group related rules into folders. • Separate development, staging, QA, and project-specific configurations. • Enable or disable testing configurations as needed. Dynamic Variables Use reusable variables in supported rules and configurations. Built-in dynamic values can generate UUIDs, timestamps, dates, and random numbers. Custom variables can also be created for environment-specific testing values. Import and Configuration Import supported API and network-testing configurations to quickly create development and QA profiles. Imported data is processed locally in the browser and can be reviewed and modified before use. Tab-Scoped Testing Where supported, rules can be limited to a specific browser tab so testing configurations can be isolated from unrelated browsing sessions. Manifest V3 HeaderCraft is built for Chrome's Manifest V3 platform and uses Chrome's supported declarative networking capabilities for configured request modifications and URL redirects. PRIVACY HeaderCraft is designed to operate locally in the browser. User-created configurations and testing data are stored locally unless a feature requires access to browser data for its intended functionality. HeaderCraft does not use third-party advertising, analytics, or tracking services and does not operate a cloud service for collecting user testing configurations. PERMISSIONS HeaderCraft requests permissions required for its developer and QA testing functionality. • Network permissions are used to apply configured network rules and redirects. • Storage is used to save testing configurations locally. • Cookies are used by Cookie Vault for supported authenticated testing workflows. • Alarms are used for scheduled local extension tasks. HeaderCraft is intended for developers, QA engineers, and other users who need to test web applications and network behavior directly in Chrome.