Most bookmarks take you somewhere. A bookmarklet does something to the page you're already on — saves it to your reading list, strips the clutter, copies the title and URL in a format you can paste, sends it to an archive.
They've been around for decades, they still work in every major desktop browser, and they've quietly become more interesting again as people get warier about installing extensions. A bookmarklet installs nothing, requests no permissions, and syncs with your bookmarks like any other link.
Here's what they are, how to add one, and where the sharp edges are.
What a Bookmarklet Actually Is
A normal bookmark stores an address like https://example.com. A bookmarklet stores a small piece of JavaScript instead, using the javascript: scheme:
javascript:(function(){ /* do something to this page */ })();
When you click it, the browser runs that code in the context of the page you're currently viewing. That's the whole trick — and it's also the entire security story, which we'll come to.
The most common pattern is a "send this page somewhere" bookmarklet, which reads the current URL and title and opens a service with them attached:
javascript:window.open('https://your-service.example/save?url='
+ encodeURIComponent(location.href)
+ '&title=' + encodeURIComponent(document.title));
That's the shape of nearly every "Save to ___" button a service offers. The encodeURIComponent calls matter: without them, any URL containing & or ? breaks the link it's being pasted into.
How to Install One
Two minutes, once you know where the fields are.
- Show your bookmarks bar. In most browsers that's a toggle in the View or Bookmarks menu, or a keyboard shortcut. Bookmarklets are only convenient if they're visible.
- Create a new bookmark. Right-click the bookmarks bar and choose to add a page or bookmark. In some browsers it's easier to bookmark any page first, then edit it.
- Name it something short. Bookmarks bar space is scarce — "Save", "Read", "MD" beat "Save this page to my reading list".
- Paste the code into the URL field, replacing whatever address is there.
- Save, then test it on an ordinary web page.
Many services offer a bookmarklet as a draggable button — you drag it straight to the bar and skip all of that. Where they do, use it: dragging avoids the copy-paste mistakes that produce a bookmarklet which silently does nothing.
Because they're just bookmarks, they sync with your browser profile like everything else in your bookmarks. Set one up on your laptop and it appears on your desktop.
What They're Genuinely Good For
Bookmarklets earn their place on tasks that are small, repetitive, and page-specific:
- Capture. Send the current page to a read-later service, a bookmark manager, or a notes app — the classic use, and still the best one.
- Copy a formatted link. Grab the title and URL together as Markdown or HTML, so pasting into notes gives you a real link instead of a bare address.
- Clean up a page for reading. Strip fixed headers and overlays that reader modes miss.
- Send to an archive. Push the current page to a web archive so a copy survives when the original disappears — a practical hedge against link rot.
- Search the current site. Run a site-scoped search from wherever you are.
- Look up the selected text in a dictionary, a translator, or a search engine.
Where they're not the right tool: anything that needs to run continuously, react to page loads, modify requests, or store data long-term. That's extension territory, and pretending otherwise leads to fragile hacks.
| Bookmarklet | Extension | |
|---|---|---|
| Install | Add a bookmark | Install from a store, grant permissions |
| Runs | Only when you click it | Can run automatically, in the background |
| Permissions | Whatever the page can do, at that moment | Whatever you granted, ongoing |
| Syncs | With your bookmarks | With your browser account, where supported |
| Updates | Never, unless you replace it | Automatically, including changes of ownership |
That last row deserves a mention. A bookmarklet is frozen — it does exactly what it did the day you added it. Extensions update, and an extension that changes hands can change behaviour without you noticing. Fewer moving parts is a genuine advantage.
The Safety Rules
A bookmarklet runs with the same access as the page you're on. It can read what's on the page — including anything you're logged into — and act as you within that page. That is a real capability, so treat the code the way you'd treat any program.
Three rules:
- Only install bookmarklets from a source you trust, ideally the service they belong to. A "handy tool" from an anonymous forum post is code you're about to run on your logged-in banking session.
- Read what it does, or don't use it. You don't need to be a developer — but a one-line bookmarklet that opens a URL with your current address attached is legible, and a 40-line obfuscated blob is not. If it's unreadable and you can't verify the source, skip it.
- Be deliberate on sensitive pages. Banking, health portals, work admin systems. There's no reason to click a third-party bookmarklet while you're inside one.
Two practical notes on top of that. Some sites block inline scripts through a strict content security policy, and bookmarklets simply won't run there — that's the site protecting itself, not a fault to work around. And a bookmarklet cannot do anything on a page you haven't loaded, which naturally limits the blast radius compared with an extension holding broad permissions.
Mobile: Possible, Awkward
Desktop is where bookmarklets shine. On mobile it's clumsier:
- On iOS Safari you can add one by saving any bookmark and then editing its address to the
javascript:code — then it's available from the bookmarks menu. - On Android, some browsers let you trigger a bookmarklet by typing its bookmark keyword or name in the address bar.
- Neither is as convenient as the native share sheet, which most capture services support directly.
Honest advice: on a phone, use the share sheet. Keep bookmarklets for the desktop, where the bar is one click away.
Keeping Them Organised
Bookmarklets go stale like everything else in a bookmarks bar. Two habits:
- Keep only what you click. Four bookmarklets you use daily beat fifteen you scroll past. Everything else goes in a folder called "Tools".
- Note where each one came from. In the bookmark's name or in a companion note. When one stops working — because a service changed its URL structure — you want to know where to get the current version rather than debugging code you didn't write.
If your bookmarks bar is already overflowing, the underlying problem is usually organisational rather than technical; our bookmarking basics guide covers structuring a library that stays usable as it grows.
Frequently Asked Questions
Are bookmarklets safe? The mechanism is safe; specific bookmarklets may not be. The code runs on the page you're viewing with that page's access, so only install ones from sources you trust, and avoid running unknown ones on sensitive sites.
Do bookmarklets still work in modern browsers? Yes, in all major desktop browsers. Individual sites with strict content security policies can block them, and mobile support is limited and fiddly.
How is a bookmarklet different from an extension? A bookmarklet is a bookmark you click that runs once; an extension is installed software with ongoing permissions that can act automatically. Bookmarklets are lighter and more limited.
Can I write my own?
Yes — if you can write a line of JavaScript, you can write a bookmarklet. Prefix it with javascript:, keep it on one line, and wrap it in a function so it doesn't leave variables behind on the page.
Why did my bookmarklet stop working? Usually the destination service changed its URL format, or the site you're on blocks inline scripts. Re-copying the current version from the service fixes the first; nothing fixes the second, and that's fine.
Small Tools, No Install
Bookmarklets are the least fashionable useful thing in a browser: no store, no permissions dialogue, no updates, no telemetry. For "capture this page" and "reformat this link", they're still the fastest route from seeing something to keeping it.
If capture is the job you're really trying to solve, it's worth picking the destination first — see the best read-it-later apps on BookmarkClup and then add whichever bookmarklet it offers.
