# Server-side rendering

Whether the content exists before JavaScript runs. Most agents never run it.

**[Content](/docs/content)** · checked on every URL · 3 checks that can fail it

Many crawlers and answer engines read only the raw HTTP response, so content that appears after hydration is invisible to them. This is measured as a heuristic comparison of the raw body against the rendered DOM, not as a spec check.

## Adoption

**Web baseline** (L4)

Standard equipment on the web. Its absence is the exception rather than its presence. Direction of travel: ► flat, as of 2026-07-28.

The default posture of every mainstream framework, and long-standing Google JavaScript-SEO guidance.

## What we check

Absence is never a finding: every check below runs only once `ssrPresent` is true, so a site that has not
adopted this is not assessed on it and appears in no report.

| Check | Kind | Raises | On whose authority |
|---|---|---|---|
| `ssrPrimaryContentEmpty` | high severity | usability | inference |
| `ssrContentOnlyAfterJs` | high severity | usability | inference |
| `ssrBoilerplateOnly` | medium severity | usability | inference |
| `ssrLowStaticShare` | informational | nothing | Lumar readiness profile |

## Specifications

| Document | Revision | Kind |
|---|---|---|
| [WHATWG HTML — the main element](https://html.spec.whatwg.org/multipage/grouping-content.html#the-main-element) | Living Standard | specification |
| [Google Search: JavaScript SEO basics](https://developers.google.com/search/docs/crawling-indexing/javascript/javascript-seo-basics) | living document | guidance |

Last re-read against the published documents: 2026-08-12.