---
title: "Cache hit ratio: how to measure it and how to raise it — warmup.rocks"
description: "What cache hit ratio means, request vs. byte hit ratio, how to measure it per CDN — and seven concrete levers to raise yours above 90%."
canonical: https://warmup.rocks/blog/cache-hit-ratio
---

Metrics

# Cache hit ratio: how to measure it and how to raise it

July 2026 · 7 min read · [← All posts](https://warmup.rocks/blog/)

If you only track one CDN metric, track this one. Cache hit ratio is the share of requests answered from cache instead of your origin — it's simultaneously a speed metric (hits are 10–100× faster), a cost metric (misses cost origin compute and egress) and a resilience metric (a warm cache absorbs traffic spikes your origin can't).

## The definition — and its two flavors

```
Request hit ratio = cache hits / total cacheable requests
Byte hit ratio    = bytes served from cache / total bytes served
```

**Request hit ratio** tells you how often users get the fast path. **Byte hit ratio** tells you how much bandwidth your origin is spared — a few large video misses can tank it while the request ratio looks great. For web performance work, the request ratio on _HTML documents_ is the number to obsess over: assets are usually cached well already; HTML is where misses hurt and where most sites do worst.

## What counts as a hit?

CDNs report more than HIT and MISS. The statuses worth knowing (Cloudflare vocabulary, other CDNs have equivalents):

| Status | Meaning | Counts as |
| --- | --- | --- |
| `HIT` | Served from edge cache | hit |
| `MISS` | Not in cache, fetched from origin, stored | miss |
| `EXPIRED` | Was cached, TTL ran out, revalidated at origin | miss |
| `REVALIDATED` | Stale entry confirmed still fresh (304) | cheap miss |
| `DYNAMIC` | Cloudflare decided not to cache (default for HTML!) | not cacheable |
| `BYPASS` | Response opted out (`no-store`, cookies) | not cacheable |

A subtle trap: `DYNAMIC` requests often aren't counted in the "cached" denominator at all, so dashboards can show a flattering ratio while every HTML request goes to origin. Check the ratio _for HTML specifically_.

## What's a good number?

Rules of thumb from CDN vendors and practice: static assets should sit at **95%+**; HTML on a well-configured site can reach **85–95%**; a byte hit ratio above 90% is healthy. If your HTML hit ratio is below 50%, there's almost always low-hanging fruit — usually one of the seven levers below.

## Seven levers to raise it

1.  **Make HTML cacheable at all.** Cloudflare doesn't cache HTML by default. You need a Cache Rule (or `Cloudflare-CDN-Cache-Control` from the origin) plus purge-on-publish so freshness doesn't suffer.
2.  **Extend TTLs.** Every TTL expiry is a future miss. If you can purge on content change, edge TTLs of days are safe — freshness comes from purges, not short TTLs.
3.  **Kill cache-busting variance.** Query strings (`?utm_source=…`), unnecessary `Vary` headers and per-visitor cookies each multiply cache keys or block caching entirely. Normalize the cache key.
4.  **Enable tiered caching.** Misses at small edge locations get answered by upper-tier hubs instead of your origin — turning global misses into regional hits.
5.  **Use stale-while-revalidate.** Serving a slightly stale copy while refreshing in the background converts would-be misses into instant responses.
6.  **Warm the long tail.** Popular pages stay warm organically; the hundreds of pages with a few daily visits each are permanently cold without help. This is where [cache warming](https://warmup.rocks/blog/what-is-cache-warming) moves the aggregate number most.
7.  **Re-warm after purges.** Deploys and purges legitimately empty the cache. A warming pass right after brings the ratio back in minutes.

## Measuring it per edge location

A global hit ratio hides geography. Your top markets keep their colos warm; everywhere else runs cold — and the global average looks fine. Slice by colo (Cloudflare: the `cf-ray` suffix; Fastly: `x-served-by`; CloudFront: `x-amz-cf-pop`) to see where visitors actually get misses. That per-colo view is also the honest way to judge whether warming works: the ratio should rise in the locations you warm, run over run.