How do pasting HTML and fetching a URL differ?

Pasted HTML stays in your browser, making it suitable for private pages or rendered source. URL fetching sends the supplied URL to an isolated server that retrieves public HTML without cookies, authorization headers, or JavaScript execution. Both sources use the same analysis logic, but their contents may differ.

How do I check a client-rendered site?

View Source shows the HTML the server returned, without anything JavaScript added. Instead, open DevTools, right-click the ` ` element in the Elements panel, and copy the outer HTML — that is the rendered result, which is also what a crawler sees after its rendering pass.

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HTML SEO Analyzer

Paste page source to check the title, description, canonical, heading structure, structured data, and image alt text at once.

Input

HTML source

Page URL (optional)

Fetch from a URL

Fetching is performed by our server. Only the HTML source is read; the target's JavaScript is never run and no cookies are forwarded.

URL to fetch

0Errors

7Warnings

3Passed

Findings

Title display width is only 12, which is short — consider adding descriptive words.
No favicon detected.
No og:title, so social platforms will decide the shared title themselves.
No og:image, so shares will have no preview image.
1 / 1 images are missing alt text.
No JSON-LD structured data detected.
Around 16 words of body text, which is thin.
Description length is reasonable (display width 36).
Canonical set: https://example.com/page
H1: 主標題

Page details

Title: 範例頁面標題
Description: 這是一段範例描述，用來示範檢查結果。
canonical: https://example.com/page
lang: zh-TW
robots: —
Body words: 16
Images: 1 (Errors: 1)
Links: Internal 0 · External 0 · nofollow 0

Heading outline

h1 主標題
h2 次標題

About this tool

Paste page HTML to review titles, descriptions, canonical, robots, language, the H1–H6 outline, social tags, structured data, and image alt text. Pasted content is analysed locally. Alternatively, expand Fetch from a URL to retrieve public HTML through an isolated server for browser-side analysis. Retrieved content is never executed as a page.

How it works

Press Ctrl/Cmd + U in the browser, select all, and copy.
Paste it in, optionally with the page URL so internal and external links can be told apart.
Read the findings, ordered errors first.

Limits and notes

Pasted HTML is analysed locally. Optional URL fetching retrieves HTML through an isolated server. Neither mode executes JavaScript; paste rendered source for dynamic pages.

Privacy

Anything you paste is analysed in this browser only. If you use “fetch from a URL”, that URL is sent to our server, where an isolated process retrieves the HTML source and hands it back to your browser for analysis. What is fetched is not stored or written to an analytics event, no cookies or authorization headers are forwarded, and the target's JavaScript is never run. The retrieved source is only ever parsed, never rendered as markup.

Frequently asked questions

How do pasting HTML and fetching a URL differ?: Pasted HTML stays in your browser, making it suitable for private pages or rendered source. URL fetching sends the supplied URL to an isolated server that retrieves public HTML without cookies, authorization headers, or JavaScript execution. Both sources use the same analysis logic, but their contents may differ.
How do I check a client-rendered site?: View Source shows the HTML the server returned, without anything JavaScript added. Instead, open DevTools, right-click the `<html>` element in the Elements panel, and copy the outer HTML — that is the rendered result, which is also what a crawler sees after its rendering pass.

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