# Back Forward Cache

> Back Forward Cache is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Use when reviewing navigation performance, browser lifecycle events, or resume-from-memory behavior. Check the actual browser lifecycle and restore path, not only static code patterns.

- Skill name: `back-forward-cache`
- Category: [Testing & Quality](https://www.openparable.com/skill/testing-quality/1)
- Source: https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/back-forward-cache/SKILL.md
- Repository: thedaviddias/Front-End-Checklist (73,218 GitHub stars when collected)

## SKILL.md

# Optimize pages for back/forward cache

Back/forward cache turns many browser back and forward navigations into near-instant restores because the entire page is resumed from memory instead of being rebuilt from the network. Losing bfcache eligibility makes common navigations feel far slower than they need to.

## Quick Reference

- Never add an `unload` listener - it is the most common bfcache blocker
- Use `pagehide` and `pageshow` instead of assuming every navigation reloads
- Refresh time-sensitive state when `pageshow.persisted` is `true`
- Keep `beforeunload` conditional and remove it when there are no unsaved changes
- Verify eligibility in DevTools instead of assuming a page is cacheable

## Check

Review this route for back/forward cache blockers. Search for unload or unconditional beforeunload listeners, state that assumes every navigation is a full reload, and resource lifecycles that break when the page is resumed from memory.

## Fix

Replace unload logic with pagehide and pageshow handlers, remove unnecessary blockers, and refresh only the time-sensitive state that must change after a bfcache restore.

## Explain

Explain how the back/forward cache differs from HTTP caching, why unload blocks it, and how pageshow/pagehide should be used instead.

## Code Review

Review route code, global listeners, analytics hooks, and data-refresh logic related to Optimize pages for back/forward cache. Flag exact listeners, APIs, or lifecycle assumptions that prevent a restore or leave stale state after a restore.

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For full implementation details, code examples, and framework-specific guidance,
see `references/rule.md`.

Rule page: https://frontendchecklist.io/en/rules/performance/back-forward-cache

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Source: https://www.openparable.com/skill/testing-quality/back-forward-cache (OpenParable). Cite the canonical URL above.