Martin JørgensenGreasemonkey – customize the web with userscripts.
Greasemonkey is a powerful, free add-on for Firefox that lets you change and enhance the functionality and appearance of websites using small custom JavaScript snippets—called userscripts. That means you can tailor your favorite websites to your own needs and preferences.
What can Greasemonkey do?
With Greasemonkey, you can:
- Change layout and appearance on websites (e.g., switch Wikipedia to dark mode)
- Remove ads or distractions
- Add extra features such as download buttons on YouTube or link previews
- Automate repetitive actions, e.g., autofill or sorting
You don’t need to code. There are thousands of ready-made scripts online (including at https://greasyfork.org) that you can install with a single click.
Examples of popular scripts
- Google in two columns: Display search results side by side
- YouTube enhancements: Skip intros or remove recommendations
- Wikipedia clean view: Make pages easier to read
How to get started
- Install Greasemonkey from Firefox Add-ons.
- Visit a userscript portal such as GreasyFork.
- Click "Install" on the desired script.
- The script activates automatically the next time you visit the site.
Tips for Greasemonkey
Use it with Firefox Developer Tools if you want to start editing scripts yourself.
Check reviews and download counts before installing a script.
You can toggle scripts on and off directly from the Greasemonkey icon in the browser.
🧠 Top five tips and tricks for Greasemonkey
1. Install scripts directly from GreasyFork
Visit https://greasyfork.org/da to find userscripts for YouTube, Facebook, Reddit, and Google. Just click "Install" to add the script to your browser via Greasemonkey.
2. Customize websites with your own scripts
Want to hide specific elements on a website, such as ad banners or annoying pop-ups? Write your own scripts in JavaScript to gain full control over how pages are displayed.
3. Use @include and @exclude to control where scripts run
When writing or editing scripts, use @include and @exclude in the metadata block to limit a script’s effect to specific domains or pages. This improves both speed and security.
4. Debug your scripts with the browser’s developer tools
If something doesn’t work, use the browser’s Console (F12 → Console) to view errors and test your JavaScript code directly. This is helpful when optimizing or troubleshooting scripts.
5. Keep scripts updated for functionality and security
Scripts can stop working when websites change their structure. GreasyFork and OpenUserJS often provide automatic updates—make sure auto-update is enabled in your Greasemonkey settings.
❓ Greasemonkey FAQ
What is Greasemonkey?
Greasemonkey is a free Firefox extension that lets you install small JavaScript programs (userscripts) to change and improve websites.
How is it different from Tampermonkey?
Greasemonkey is built for Firefox and focuses on security and integration with Mozilla’s ecosystem. Tampermonkey offers broader browser support (Chrome, Edge, 1) and more advanced features. Many scripts work in both.
Is it safe to use userscripts?
Yes—if you only install scripts from trusted sources like GreasyFork or OpenUserJS. Always read the code or reviews before installing.
How do I remove a script?
Click the Greasemonkey icon in the browser → "Manage scripts" → find the script → click "Delete" or "Disable".
Can I write my own scripts?
Yes! You just need basic JavaScript knowledge. Greasemonkey includes a built-in editor where you can start with an @metadata template and build from there.
