js-render-check

js-render-check is a skill for Claude Code from PavloSEO/seohead-seotools. It costs 153 tokens per session (1,161 once invoked), scanned A, original, MIT.

A comparison between a page’s raw HTML and the page after JavaScript runs. JavaScript is code that can add or change page content after the initial document loads.

In plain words
What is it for?
Use it to investigate JavaScript-heavy sites, single-page applications, differences between rendered and unrendered crawls, or missing links and content.
Why use it?
It shows whether important text, links, headings, metadata, or structured data exist only after rendering. That matters because search crawlers may see the initial page before they process its scripts.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to investigate JavaScript-heavy sites, single-page applications, differences between rendered and unrendered crawls, or missing links and content.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/pavloseo/seohead-seotools/js-render-check
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add PavloSEO/seohead-seotools --skill js-render-check
Clone the repo
git clone --depth 1 https://github.com/PavloSEO/seohead-seotools

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for js-render-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/pavloseo/seohead-seotools/js-render-check/github.svg)](https://agentmods.dev/skills/pavloseo/seohead-seotools/js-render-check)
Your own site
<a href="https://agentmods.dev/skills/pavloseo/seohead-seotools/js-render-check"><img src="https://agentmods.dev/badge/skills/pavloseo/seohead-seotools/js-render-check/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for js-render-check

Your own site · 80×15
<a href="https://agentmods.dev/skills/pavloseo/seohead-seotools/js-render-check"><img src="https://agentmods.dev/badge/skills/pavloseo/seohead-seotools/js-render-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 153 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,161 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00153 $0.01161
Opus 5 $0.00077 $0.00580
Sonnet 5 $0.00031 $0.00232
Haiku 4.5 $0.00015 $0.00116

Measured 8d ago against content hash 6d90a14616bc, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

js-render-check scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

**One command instead of manually using curl and headless Chrome:**
.claude/skills/js-render-check/SKILL.md · 96 lines

How it starts

The opening of the file, as written. The whole thing — 96 lines — stays where its author put it; the contents beside it link to each section on GitHub.

JS Render Check — What Is Visible on the Page Only After JavaScript

Screaming Frog measures one snapshot—raw or rendered, depending on whether JS Rendering is enabled—but does not compare "before JS" with "after JS." This skill performs exactly that diff.

When to Use It

  • "Do content / links / metadata appear only after JS?"
  • SPA / Next.js / Nuxt / CSR: "Will it be indexed?" or "Is SSR required?"
  • An SF crawl differs with JS Rendering enabled versus disabled, and you need to determine which count is correct.
  • A regional or silo audit found zero links where links are known to exist.

Workflow

One command instead of manually using curl and headless Chrome:

seohead render-check --url https://example.com

Use a mobile viewport and device emulation where the layout differs:

seohead render-check --url https://example.com --viewport mobile

Returned fields:

Field Meaning
raw / rendered identically calculated snapshots of both documents: words, internal links, title, h1, canonical, JSON-LD types, and size
empty_shell ID of an empty single-page application container, if present
js_dependent whether the page depends on scripts in any way
metrics_lab TTFB, FCP, LCP, CLS, load, and weight—lab data, not field data
findings ready-to-use written conclusions

How to Interpret Findings

Finding Severity Action
"empty <div id="root"> container" critical use SSR or prerendering: without rendering, the bot sees an empty page
"N% of text appears only after JS" critical when >50% move the primary content into the server response
"links appear only after JS" critical site traversal breaks: the crawler cannot reach deeper pages
"title is changed by a script" critical an unpredictable title may appear in search results
"canonical is injected by a script" critical the directive must not depend on rendering
"Schema.org appears only after JS" warning rich results are uncertain
"rendering changes nothing" okay SSR works; no further investigation is needed

Read the full file on GitHub · 96 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 96 lines · 153 tokens per session scan A 6d90a14616bc

Subscribe to this mod's changes

js-render-check is a skill published in the GitHub repository PavloSEO/seohead-seotools (0 stars, last pushed 5d ago), licensed MIT. It adds 153 tokens to every session and 1,161 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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