Skip to content

Performance

My HTML document is too large

Large documents are usually server-rendered state inlined into the page — a framework payload, an unfiltered API response, or base64 images. The browser has to download and parse all of it before it can render, and none of it is cacheable separately.

What 13x checks

This is rule performance.document-size in the public registry: HTML document is a reasonable size. It runs on every audit, against the pages we actually fetched, and its result is derived from the response rather than estimated.

Surface
Performance
Score weight
4 of the readiness score
Scope
Runs on every audited page
Applies
To every site

Registry version 2026-07-30. Every rule is published, and the audit is deterministic — the same page produces the same finding every time.

The fix

The same text the audit hands you when this check fails on your own site.

The HTML document is KB before any assets load. The browser downloads and parses all of it before rendering, and none of it is cacheable separately.

The usual causes, in order of how often they turn out to be it:

1. Server-rendered state inlined into the page — a framework payload, or an API response embedded whole when the page needs four fields from it. Select only what you render. 2. Base64 images in the markup. They cannot be cached, cannot be lazy-loaded and inflate by a third. Serve them as files. 3. A large list rendered in full — hundreds of rows, or every option in a select. Paginate or virtualise. 4. Inlined critical CSS that grew past the point where inlining helps.

Find the bulk:

bash code
curl -s https://example.com | wc -c
curl -s https://example.com | grep -o 'data:image[^"]*' | wc -c   # base64 total

Framework-specific versions

Where the change differs enough to be worth writing out separately.

Does your site have this problem?

13x checks this and 112 others against your live URL in about 30 seconds. No account, and every finding comes with the fix for your framework.

No signup. Results in 30 seconds.

More performance checks