# API HTTP Caching Conditional Requests

> Apply HTTP caching and conditional requests for REST APIs: Cache-Control, ETag, If-None-Match 304, and private vs public caches. Use when optimizing GET performance or reviewing cache headers.

- Skill: `deangrant/api-http-caching-conditional-requests` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add deangrant/api-http-caching-conditional-requests`
- Raw SKILL.md: https://api.skillmd.com/api/skills/deangrant/api-http-caching-conditional-requests/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: deangrant (https://skillmd.com/u/deangrant)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/deangrant/api-http-caching-conditional-requests

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# HTTP Caching and Conditional Requests

Use this skill when making **safe GETs** cheaper via caches and validators.

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## 1. Cache-Control

Common directives: `max-age`, `s-maxage` (shared), `private` / `public`,
`no-store`, `must-revalidate`, `stale-while-revalidate`.

User-specific data: `private` + `Vary: Authorization` (or equivalent).

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## 2. Validators

Strong **ETag** (or `Last-Modified`). Client sends `If-None-Match` → **304**
when unchanged. Pair with caching for revalidation.

Mutations and contested updates use `If-Match` (see conditional-requests skill).

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## 3. Quick checklist

- [ ] Cache-Control correct for public vs private data.
- [ ] ETag or Last-Modified on cacheable GETs.
- [ ] 304 path implemented.
- [ ] Vary set when representation differs by header.
- [ ] No caching of sensitive responses on shared caches.

See [reference.md](reference.md) and [examples.md](examples.md).