WebLab FAQ

Answers about WebLab, from the first line of code to a minified website.

Last Updated: November 11, 2026

1. Basics

Q1: What is WebLab?

A1: A free online editor for HTML, CSS and JavaScript that runs in your browser. You write code in three boxes and see the page beside it as you type, with a console underneath. It also minifies and formats HTML, CSS, JavaScript, JSON and SVG, one file at a time or a whole website folder at once.

Q2: Is it free, and do I need an account?

A2: It is free and there is no account or registration. Like every page on ZeroDataUpload, it is supported by advertising.

Q3: Is my code uploaded?

A3: No. Your code is run, minified and formatted by this browser on your device and is never sent to a server. The page itself, its ads and its analytics load from the internet as on any website.

Q4: What is kept in my browser?

A4: Your projects and settings are kept in this browser once you change something, so they are still there next time; looking around writes nothing. The Minify and Format box keeps its text between visits when it is no longer than 100,000 characters. Clearing this site's data in the browser removes everything.

Q5: Which browsers does it work in?

A5: Current versions of Chrome, Edge, Firefox and Safari on computers. On a phone the code, the page and the console share the screen through tabs. The gzip sizes need a browser that can compress, which every current browser can.

Q6: How is WebLab different from CodeForge?

A6: CodeForge converts data from one format to another, such as JSON to CSV, XML or YAML, and can give JSON pretty or minified as part of that. WebLab is for web pages: you write and run HTML, CSS and JavaScript, and it minifies or formats them, as well as JSON and SVG, one file or a whole folder.

2. Live editor

Q7: How does the live page work?

A7: The HTML, CSS and JavaScript boxes are joined into one page that runs beside the code. With Auto on, it runs again after you stop typing for 0.7 seconds (you can choose 0.3 or 1.5); a change to the CSS alone shows at once without a reload. Run (or Ctrl+Enter) runs it straight away.

Q8: Can I paste a whole page?

A8: Yes. Paste a complete page with its head and body into the HTML box and keep the CSS and JS boxes empty, or use Move inline style and script into the CSS and JS boxes from the box's menu to split it.

Q9: Can the code I run here reach this site or my data?

A9: No. Your page runs in a closed-off frame that does not share this site's address, so it cannot read this site's storage, its cookies or the data of other tools, and it cannot move the main page elsewhere. A page that uses localStorage gets a separate one kept with the project, up to 100,000 characters.

Q10: Can my page load files from the internet?

A10: Only if your own code links to them, for example a font, a picture or a script on another website; the tool itself adds no such links. They load inside the closed-off frame and need an internet connection. A link in your page that you click opens in a new tab.

Q11: What does the console show?

A11: What your page writes with console.log, info, warn, error, table, group, count and time, and every error with the line it came from in your HTML, CSS or JS box; click the line to jump there. Type JavaScript into the line at the bottom and press Enter to run it in the page; the arrow keys bring back earlier lines.

Q12: What happens with an endless loop?

A12: Each loop in your code checks how long it has been running. One that keeps going for more than two seconds is stopped, and the console names its line. If the page stops answering for another reason, a Stop it button appears over the preview. You can turn the loop check off in Editor settings.

Q13: Which screen sizes can I preview?

A13: Fit the space, two phones (360 by 740 and 412 by 915), a tablet upright and on its side, a laptop (1366 by 768), a full HD screen (1920 by 1080) or your own size from 100 to 4,000 pixels. The page is scaled down to fit and can be turned sideways or shown on its own.

Q14: What do the templates give me?

A14: A blank page, a starter page with a counter button, a page layout with a side menu, a photo grid, a form that checks its fields, a canvas animation, a to-do list that remembers its items and a JavaScript module with top-level await. Each opens as a new project; your current work stays in Projects.

Q15: Can I open files I already have?

A15: Yes. Open (or dropping files) takes HTML, CSS and JavaScript files, a whole folder or a zip. The main HTML page opens in the HTML box, its linked stylesheets and scripts move into the CSS and JS boxes, and its pictures and fonts are shown from the opened files.

3. Projects, saving and sharing

Q16: How are projects kept?

A16: In this browser, once you change something: up to 100 projects and 1,000,000 characters together, because every tool on this site shares the same storage. Projects lists them with the time they were changed; you can rename, copy or delete them, and back them all up to a file or bring a backup back.

Q17: How do I save my page as a file?

A17: Save as gives one HTML file with the CSS and JavaScript inside, or a zip with index.html, style.css and script.js. Copy as one HTML file puts the same page on the clipboard.

Q18: How does a share link work?

A18: Share packs the whole project into the link, in the part after #, which browsers do not send to a server. Whoever opens the link gets a copy in their own browser, kept in their Projects once they change it. Long projects make long links; over 1,000,000 characters, use Save as instead.

Q19: What if my project is too big to keep?

A19: It still opens and runs, but it is not kept in this browser, and a message says so. Keep it with Save as, or make room by deleting old projects.

4. Minify and Format

Q20: What does minifying change?

A20: Gentle removes comments and spaces. Balanced also shortens colours, numbers and quotes and joins CSS rules that sit together. Smallest also drops optional closing tags and goes over JavaScript more times. Each change keeps what the page shows and does; Smallest may stop the code passing a validator.

Q21: Which languages can I minify?

A21: HTML (with the CSS and JavaScript inside it), CSS, JavaScript, JSON (also with comments and trailing commas, which are removed) and SVG. SCSS, Less and JSX are minified as CSS or JavaScript; TypeScript must be turned into JavaScript first.

Q22: What are the JavaScript options?

A22: Shorten variable names (on by default), also the top-level names, keep function or class names, remove console calls or debugger statements, keep licence comments, the newest JavaScript the result may use (ES5 to ES2020), a source map, and writing non-English characters as escapes.

Q23: What is the gzip size?

A23: Most web servers compress files with gzip or a similar method before sending them, so the gzip size is close to what a visitor downloads. It is shown before and after minifying, so you can see how much the minifying itself saves.

Q24: Which languages can I format?

A24: HTML, CSS, SCSS, Less, JavaScript, JSX, TypeScript, JSON and Vue files, with 2 spaces, 4 spaces or tabs, a line length of 80, 100, 120 or 160 characters, and under More options the quotes, semicolons, trailing commas and how spaces between HTML tags are treated.

Q25: What happens when my code has a mistake?

A25: The result shows what is wrong and on which line and column, with a button that takes you there; the line is underlined in your code. Nothing is changed in your code.

5. Many files

Q26: How do I minify a whole website?

A26: Open Many files and drop the website folder or a zip of it, or choose files or a folder. Press Minify all (or Format all). Every HTML, CSS, JavaScript, JSON and SVG file is done with the settings of the Minify or Format tab, and Download everything as a zip gives you the whole site back with its folders.

Q27: What happens to pictures, fonts and other files?

A27: They are copied into the zip as they are, unless you untick Put the other files in the zip too. Files already named .min.js or .min.css are copied, not minified again.

Q28: How many files can I add?

A28: Up to 5,000 files or 500 MB at once. A file larger than 25 MB is copied as it is. Files in a zip that are protected with a password or damaged are left out, and a message says how many.

6. Privacy and help

Q29: Does it work offline?

A29: The page must load from the internet first. After that, writing, running, minifying and formatting all happen in the browser, but the page does not install itself for offline use.

Q30: Can I use it with the keyboard?

A30: Yes. Tab reaches every button and box, and the code boxes keep Tab for indenting and shorthand (press Escape, then Tab, to move on). While you use the tool, Ctrl+Enter runs the page or minifies, Shift+Alt+F formats, Ctrl+S keeps the project, F3 finds and replaces, Ctrl+/ comments lines and ? opens the help.

Still have a question?

The help page walks through every part of WebLab. For anything else, use the contact form.