Replay
Time-travel debugger that gives agents deterministic runtime recordings.
About
Replay is a time-travel debugger for web applications. Its recording browser captures a deterministic, DVR-style recording of the entire browser session: every DOM change, network request, JavaScript execution frame, and state update. You can then step backward and forward through any point in the session, inspect variables and call stacks as they were, and add print statements retroactively.
Its 2025 push is agentic: Replay MCP exposes the same time-travel debugging capabilities to coding agents, so an agent can open a recording, add logpoints, pull stack traces and screenshots, and deliver a root cause with a suggested fix instead of guessing from error messages. It integrates with Playwright and Cypress for flaky test debugging and records CI failures deterministically.
What it can do
- Deterministic full-session browser recordings
- Time-travel debugging with retroactive print statements
- Replay MCP for agentic root-cause analysis
- Playwright and Cypress test recording
- Shareable recording URLs for collaborative debugging
Setup
npm i -g replayio, then replayio record <url> or record-suite to capture Playwright and Cypress runs.
Prerequisites
Node.js for the CLI; a browser app or test suite to record.
Use cases
Works with
Trust score — 8/10
Scored 8/10 (verified tier, metrics-v1). Evidence: Verified via vendor site/docs/GitHub and reputable coverage, wave 90; Trending score 84/100 from researcher assessment.
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.