Test and preview HTML code.
Paste HTML and watch it render as you type, with your CSS and scripts working the way they will on a real page.
- Livepreview as you type
- 3 widthsdesktop, tablet and phone
- 1 clickto a link, once signed in
Loading the tool…
How it works
From markup to a working link in three steps.
Paste it, open it or drop it in
Type or paste markup, open an .html file, or drag one onto the editor. Sample loads a page to try.
Check it at every width
Switch between desktop, tablet and phone. The editor flags mismatched and unclosed tags, and the console shows what your scripts log and where they fail.
Get a link
Press Get a link and the page goes live at a nudgehost.com address. Signed out, you make a free account first. On the free plan the link lasts 14 days.
In the tester
What the tester does.
- Syntax highlighting
HTML, and the CSS and JavaScript inside it, in their own colours, with line numbers and folding.
- Error flags
Mismatched and unclosed tags are marked beside the line as you type.
- Console
What your scripts log, and uncaught errors with their line number.
- Three widths
Desktop, tablet at 768px and phone at 375px.
- Full screen
Open the preview over the whole window.
- Open or drop a file
Open an .html or .htm file up to 2MB, or drag one onto the editor.
- Format
Re-indent messy markup in one click.
- Copy, download, clear
Copy the markup, save it as an .html file, or start again.
- Counts
Characters, lines and bytes, updated as you type.
- Dark editor
Switch the editor to a dark theme, and the tester remembers it.
- Sample
A small page with a script, ready to edit.
- Get a link
Publish the page to a nudgehost.com link from a free account.
Sharing it
The page you tested, live at its own link.
Press Get a link and the page goes online. Paste the address into a chat or an email and it opens as a working page, scripts included. On the free plan the page stays up for 14 days.
- A preview card with your page’s title
- Opens as a working page, scripts included
- No account needed to open it
Compared
NudgeHost and Static.app, for testing HTML.
Both testers are free, run in the browser and redraw the page as you type. The rows below set the two side by side.
| NudgeHost | Static.app | |
|---|---|---|
| Live preview as you type | Yes | Yes |
| Open or drag in an .html file | Yes | Yes |
| Syntax highlighting | Yes | Yes |
| Error flags in the editor | Mismatched and unclosed tags | No |
| Console for script output | Yes, with line numbers | No |
| Desktop, tablet and phone widths | Yes | Yes |
| Format, copy and download | Yes | Yes |
| Full-screen preview | Yes | Yes |
| Dark editor | Yes | Yes |
| A link to the tested page | One click from a free account | Not from the tester. Its upload box takes a ZIP, a PDF or an image, not an .html file |
Static.app checked on static.app/html-test on 27 September 2026.
Testing HTML
Why test HTML here.
A preview tells you the page works. Sharing it usually means copying the markup somewhere else first. Here the editor that shows the page can publish it as a working HTML page with one press, and the link opens for anyone.
Pages written by AI tools are a good fit. A page Claude built as an artifact often needs a quick check before it goes out, and a mismatched tag or a script error shows up here before anyone else sees it.
The preview runs your scripts but blocks pop-ups, forms and alerts, so nothing on the page can take over the tab. When the markup already lives in a file, the HTML file viewer opens it straight from disk. NudgeHost's free plan keeps 3 published pages live at once, each for 14 days.
Guides
Pages worth testing here.
Frequently asked questions
Is the HTML tester free?
Yes. The editor, the preview, the error flags and the console need no account and cost nothing. Publishing a page with Get a link is free as well, on a free account with no card.
Does my HTML get sent to a server?
Not while you test. The editor, the preview, the error flags and the console all run in this page. Your markup is sent to NudgeHost only when you press Get a link to publish it.
Do styles and scripts actually run?
Yes. CSS in a style tag or a style attribute applies, and JavaScript in a script tag or an inline handler runs, the same way it would in a browser tab. What a script logs appears in the console under the preview.
Is it safe to paste code someone sent me?
The preview is sandboxed on a separate origin with no access to this page, its cookies, or your NudgeHost account. That contains what the snippet can do here, though it is still worth reading anything unfamiliar before running it somewhere that matters.
Can I open an HTML file from my computer?
Yes. Use Open file, or drag an .html or .htm file onto the editor. The tester opens files up to 2MB, the same limit as the HTML viewer, and Download saves your edits under the same file name.
Does the tester find errors in my HTML?
It flags two kinds of mistake as you type. One is a closing tag that does not match the element it meets, such as an h1 heading closed with an h2 tag. The other is an element that needs a closing tag and never gets one. Closing tags that HTML lets you leave out, such as those for paragraphs and list items, raise nothing. It is not a full validator, so it does not check attributes or which elements may sit inside which.
What does the console show?
Everything the page passes to console.log, console.info, console.warn and console.error, plus uncaught errors and rejected promises. Each entry shows the line it came from when the browser reports one. The console keeps the first 200 entries each time the preview reloads, each cut to 1,000 characters.
Why doesn't alert() work in the preview?
The preview runs scripts but blocks alerts, pop-ups and form submissions, so a page cannot take over the tab or send you somewhere else. Use console.log instead and read the result in the console.
What do the three preview widths do?
Desktop fills the preview pane. Tablet sets the page to 768px wide and Phone to 375px, so layouts that change with the screen width show up. When the pane is narrower than the width you chose, the preview scrolls sideways inside it.
What does Format change?
Format re-indents the markup with two spaces per level. It changes the spacing and line breaks and leaves the tags alone, so it will not fix a mismatched tag for you.
Can I test a page an AI tool wrote?
Yes. Paste the HTML an assistant produced and the preview shows whether it renders, the flags point to any mismatched or unclosed tags, and the console shows whether its scripts fail.
Can I test a form?
The preview blocks form submission, so pressing a submit button there does nothing. A published page allows forms, so once the link is live you can try a form that sends to an outside service.
Which keyboard shortcuts work in the editor?
Undo and redo work as they do in any text box, Tab indents the selected lines and Shift+Tab takes the indent away. The small arrows beside the line numbers fold a block of markup out of sight. Typing the angle bracket that ends an opening tag adds its closing tag for you.
Can I use separate CSS and JavaScript files?
Everything goes in one HTML document, with CSS in style tags and JavaScript in script tags. A stylesheet or script linked by its full https address loads in the preview. A file referenced by a relative path, like style.css next to your page, has nowhere to load from.
Does the tester save my work?
No. The markup lives in this page until you leave it, and reloading brings back the sample. Use Download to keep a copy as an .html file, or Get a link to put it online. The only thing the tester remembers is whether you chose the dark editor.
How do I share the page I tested?
Press Get a link. The page goes live at a nudgehost.com address that anyone can open, and the Copy link button puts the address on your clipboard, ready to paste into a chat, an email or a document.
Can I change a page after I publish it?
Pressing Get a link again publishes a new copy at a new address. With an account you can replace the file behind a link you already shared, from your dashboard, and the address stays the same.
What does a shared link look like in a chat?
Chat apps that show link previews draw a NudgeHost card carrying your page's title, taken from its title tag. Give the page a title before you publish, so the card says what it is.
How long does a published link last?
14 days on the free plan. On Pro and Studio it stays up until you delete it.
How many pages can I publish on the free plan?
3 live at a time. When one ends, its slot frees up. Pro and Studio have no limit on live links. Free accounts made before 29 October 2026 keep links until they delete them, with 10 active links for accounts made before 27 October 2026 and 5 for newer ones.
How is the tester different from the HTML viewer?
The HTML viewer opens a file from your computer and shows it as it is. The tester is for changing the markup, with the preview redrawing as you type and the error flags and console beside it. Both read the file in your browser.
How big a page can I publish?
Up to 25MB on the free plan, 250MB on Pro and 1GB on Studio. The 2MB limit on Open file applies to files you open, not to what you publish.
Related tools
Other things you can do on NudgeHost.
Ready to try the dev tools?
Free forever, no credit card needed. The whole thing takes a few seconds.