Userscript Manager
Tampermonkey
Run userscripts with a built-in editor, many sync options and a site blacklist. Free; source licence not stated.
View detailsBest userscript managers for Chrome
A userscript manager runs small scripts that change websites for you. We picked three for Chrome: Tampermonkey, Violentmonkey and ScriptCat. Choose Tampermonkey for its built-in editor and many sync options, Violentmonkey if you want open source under the MIT licence, and ScriptCat for background or scheduled scripts.
Userscript manager extensions
Userscript Manager
V
Userscript Manager
Violentmonkey
Run scripts in list order and sync with four cloud services. Open source (MIT).
View details
S
Userscript Manager
ScriptCat
Tampermonkey-compatible, with background and scheduled scripts. Free and open source (GPL-3.0).
View detailsUpdated October 2026
Our picks at a glance
| Extension | Price | Open source | Manifest V3 | Sync | Special feature |
|---|---|---|---|---|---|
| Tampermonkey | Free (developer's download list) | Not stated | Yes | Chrome Sync, Google Drive, Dropbox, OneDrive, Yandex.Disk, WebDAV | Built-in editor with ESLint |
| Violentmonkey | No price shown | Yes (MIT) | Yes (needs Chrome 135+) | Dropbox, OneDrive, Google Drive, WebDAV | Scripts run in list order |
| ScriptCat | Free (official site) | Yes (GPL-3.0) | Yes | Cloud sync (services not named in our sources) | Background and scheduled scripts |
All three need you to switch on the "Allow User Scripts" toggle (Chrome 138 or newer) or Developer Mode (older Chrome) before scripts run. We confirmed this for Tampermonkey and ScriptCat from their own docs. For Violentmonkey, the developer's pages we read do not describe this step.
What is a userscript manager?
A userscript manager is a browser extension that installs and runs userscripts. A userscript is a small piece of code that changes how a website looks or works. It can hide a banner, add a button, or automate a task. The manager keeps your scripts in one place, updates them and lets you turn each on or off.
How do I choose a userscript manager?
Start with what you need. Want an editor and many sync options in one tool? Look at Tampermonkey. Prefer open source code? Look at Violentmonkey or ScriptCat. Need scripts that run in the background or on a schedule? Look at ScriptCat. All three run scripts you write or find, so the choice is about features, licence and Chrome version.
Are userscript managers safe?
A manager is only as safe as the scripts you add. A script can read and change the pages it runs on, so install scripts only from sources you trust. The managers also ask Chrome for broad access. Violentmonkey and ScriptCat list access to all sites, and ScriptCat also lists debugger. Read each install prompt.
Why do my scripts not run on current Chrome?
Chrome needs a setting turned on. The developer docs for Tampermonkey and ScriptCat say to switch on "Allow User Scripts" for the extension on Chrome 138 or newer, or Developer Mode on older Chrome. ScriptCat's docs add that you may need to disable and re-enable the extension, or restart the browser, if scripts still do not run.
Do userscript managers work with Manifest V3?
Yes, all three do. Tampermonkey's changelog has an MV3 section from version 5.3.0. Violentmonkey's official site says its store build was updated to Manifest V3, and that build needs Chrome 135 or newer. ScriptCat's manifest is Manifest V3. Manifest V3 is Chrome's current extension format.
Which userscript manager is open source?
Violentmonkey (MIT licence) and ScriptCat (GPL-3.0), both per the licence files in their GitHub repositories. The Tampermonkey developer does not state a source licence on the pages we read, so we do not claim it is open source. That is one reason people compare it with the other two.
Good to know
- Back up your scripts before you switch managers. Tampermonkey backs up to zip or cloud, and Violentmonkey exports a zip. ScriptCat says it can migrate scripts from other managers.
- Run only one manager at a time, so two managers do not both change the same page. (This is Xplorekit's own tip, not from the developers.)
Read more
Related guides: Developer tools and Web clippers and archivers.
Official sources: Tampermonkey FAQ, Violentmonkey and ScriptCat docs.
These are third-party extensions, not built or maintained by Xplorekit. We link to each official Chrome Web Store listing — install and permissions are entirely between you and the extension's own publisher.