Bookmarklets let you run small programs from your bookmark bar

A bookmarklet is a bookmark that runs code instead of opening a webpage. When you click it, it performs an action on the page you're viewing — highlight all links, change text size, remove ads, or automate repetitive tasks. On a school Chromebook, bookmarklets work the same way they do on any Chrome browser, but school restrictions may block some of them depending on what they try to do.

The key difference is that your school's network filter and device policies control what bookmarklets can actually run. A bookmarklet that works fine at home might not work at school if it tries to access blocked websites or modify system settings. This guide shows you how to create bookmarklets that will work within your school's setup, and how to troubleshoot when one doesn't.

Key Takeaways

  • Bookmarklets are saved as bookmarks but contain code that runs when you click them, letting you automate tasks without installing software.
  • You create a bookmarklet by right-clicking your bookmark bar, selecting "Add bookmark", and pasting code into the URL field instead of a web address.
  • School Chromebooks may block bookmarklets that try to access external websites, modify files, or interact with system settings.
  • If a bookmarklet doesn't work, check whether your school's filter is blocking the website it's trying to reach, or ask your IT department what restrictions apply.
  • Simple bookmarklets that work only on the current page — like text size changers or link highlighters — are most likely to work on school devices.

How to add a bookmarklet to your Chromebook

Start by opening Chrome and going to any webpage. Right-click on your bookmark bar (the row of bookmarks below the address bar). If you don't see a bookmark bar, press Ctrl + B to show it. Select "Add bookmark" from the menu that appears.

A small dialog box will pop up. In the "Name" field, type a short name for what the bookmarklet does — for example, "Bigger Text" or "Highlight Links". In the "URL" field, delete the web address that's already there and paste the bookmarklet code instead. The code will start with javascript: followed by the actual instructions. Click "Save" when you're done.

The bookmarklet now appears in your bookmark bar. Click it anytime you're on a webpage and want to run that action. Nothing installs on your device — it's just a bookmark that runs code in your browser.

Common bookmarklets that work on school Chromebooks

The safest bookmarklets are ones that only change how the current webpage looks or behaves. These don't try to download files, access other websites, or modify your device settings, so school filters rarely block them.

Text size changer: Paste this code to make all text on a page larger or smaller. Replace the number 1.2 with a higher number for bigger text (1.5, 2.0) or a lower number for smaller text (0.8, 0.9):

javascript:document.body.style.fontSize="1.2em";

Link highlighter: This code outlines all links on the page in bright red, making them stand out:

javascript:var links=document.getElementsByTagName('a');for(var i=0;i<links.length;i++){links[i].style.border='2px solid red';}

Dark mode toggle: This inverts the colors of the page to create a dark background with light text:

javascript:document.body.style.filter='invert(1)';

These bookmarklets work entirely within the webpage you're viewing and don't contact external servers, so they almost always function on school networks.

Why some bookmarklets don't work on school Chromebooks

School Chromebooks run under managed policies set by your IT department. These policies can block bookmarklets in several ways. The most common reason is that the bookmarklet tries to reach a website your school has filtered — for example, a bookmarklet that fetches data from an external service. Your school's network blocks the request before the bookmarklet can complete.

Some bookmarklets also try to download files, open new windows to specific sites, or modify browser settings. School policies often prevent these actions to protect device security and enforce acceptable use rules. A bookmarklet that works on your personal laptop may fail on your school Chromebook for exactly this reason.

You'll usually see no error message — the bookmarklet simply won't do anything when you click it. The best way to know if a bookmarklet will work is to test it on a simple page first, and if it fails, assume your school's filter or policies are blocking it rather than that the code is broken.

Testing a bookmarklet before you rely on it

Before you add a bookmarklet to your bookmark bar, test the code on a blank page or a simple website. Open a new tab and go to any webpage — Google's homepage works well. Right-click your bookmark bar and add a temporary bookmark with the bookmarklet code you want to test. Click it and see what happens.

If the bookmarklet works, you'll see an immediate change on the page — text will resize, colors will shift, links will highlight, or whatever the code is designed to do. If nothing happens, the bookmarklet either doesn't work with that particular page, or your school's policies are blocking it. Try the same bookmarklet on a different page to narrow down the problem.

If a bookmarklet works on some pages but not others, it's likely because the code relies on page elements that don't exist on every site. If it works nowhere on your school network, your school's filter or device policies are probably blocking it. In that case, you can either try a different bookmarklet that does something similar, or contact your school's IT department to ask whether the restriction can be lifted.

Bookmarklets that usually don't work on school Chromebooks

Avoid bookmarklets that try to download files, open external websites, or interact with cloud storage services. These almost always fail on school networks because they violate filtering rules or device policies. Examples include bookmarklets that save pages to Pocket, export data to Google Drive, or fetch information from APIs (application programming interfaces).

Bookmarklets that modify your browser's settings or extensions also won't work, because school policies lock down those features. Similarly, bookmarklets designed to bypass filters or access blocked content will not function — and attempting to use them could trigger alerts to your IT department.

If you find a bookmarklet online that sounds useful but doesn't work on your school Chromebook, the reason is almost always that it tries to do something your school has restricted. This is a security feature, not a limitation of bookmarklets themselves.

Where to find bookmarklets and how to read the code

Websites like Bookmarklets.com and GitHub host collections of bookmarklets organized by what they do. When you find one you want to try, look at the code before you add it. Bookmarklet code always starts with javascript: and contains instructions written in JavaScript, a programming language that runs in web browsers.

You don't need to understand the code to use a bookmarklet, but a quick scan can tell you whether it's likely to work on your school network. If the code contains words like "fetch", "XMLHttpRequest", "download", or "chrome.storage", it's trying to contact external servers or access your device's storage — and your school probably blocks it. If the code only manipulates the current page (words like "document", "style", "innerHTML"), it should work.

Always copy bookmarklet code from trusted sources. Malicious code disguised as a bookmarklet could try to steal passwords or data, so only use bookmarklets from websites you recognize or that come recommended by teachers or classmates.

Frequently Asked Questions

Can my school see what bookmarklets I use?

Your school can see which websites you visit, but bookmarklets that only modify the current page don't create separate network traffic. However, if a bookmarklet tries to contact an external server, your school's filter logs that request. If you're unsure whether a bookmarklet is allowed, ask your IT department before using it.

Will a bookmarklet I create at home work on my school Chromebook?

It depends on what the bookmarklet does. Simple ones that only change how a page looks will work on both. Bookmarklets that access external websites, download files, or use cloud services will fail on your school network because of filtering and device policies. Test it at school to find out.

What should I do if a bookmarklet stops working?

First, try it on a different webpage to see if the problem is with that specific site. If it works nowhere, your school's filter or policies are likely blocking it. You can contact your IT department to ask why, but they may not be able to remove the restriction. Try a simpler bookmarklet that does something similar instead.

Can I share a bookmarklet with classmates?

Yes. You can copy the bookmarklet code and send it to a classmate, or tell them where you found it online. They can add it to their own Chromebook the same way you did. Keep in mind that if it doesn't work for you on your school network, it probably won't work for them either.

Is it against school policy to use bookmarklets?

Using bookmarklets to change how webpages look or work is not against policy at most schools. However, using them to bypass filters, access blocked content, or circumvent security measures is. If you're unsure whether a specific bookmarklet is allowed, ask your teacher or IT department before adding it.