15 Useful Bookmarklets for Web Devs (What Are They, Anyway? 🤔)
Tags: webdev, javascript, programming, beginners
Published: 2023-12-13 19:24:42

Hey, everyone! 
Today, I want to share something with you called a Bookmarklet. What is that? Read on to find out!!

## What is a Bookmarklet?

A bookmarklet is a small piece of JavaScript code that can be saved as a bookmark in a web browser. When the bookmarklet is clicked, it executes the JavaScript code on the current webpage, performing a specific action or enhancing the functionality of the page. They're awesome! So let's find out how to make one!

## How to Make a Bookmarklet

To add a bookmarklet to your browser, make sure you can see your bookmarks bar (sometimes called a "favorites" bar). To add a bookmarklet, follow these steps:

1. Right-click on your bookmark bar and select "Add Site" or a similar option.
2. Give your bookmarklet a name.
3. Replace the address with a JavaScript code like this one:

```javascript
javascript:(function() {
  /*Your code goes here*/
})();
```

The code above is a JavaScript self-executing function. When you click on the bookmarklet, it will run. The great thing about bookmarklets is that they can interact with the page you're on. There are some important limitations of bookmarklets, though! Let's look at those below.

## Limitations to Keep in Mind

Here are some tips based on my experience to help you create effective (and functional) bookmarklets:

- **Avoid Single Line Comments:** Single line comments (`//Comment`) can be problematic and difficult to troubleshoot in bookmarklets. Since bookmarklets are only one line long, using the `//` method effectively comments out everything after it. Instead, use `/*Comment*/` to comment out multiple lines.
- **Be Aware of Cross-Origin Requests:** Depending on your browser version and settings, bookmarklets making requests to APIs may have the origin `null`. This can sometimes cause issues when making requests to APIs in a bookmarklet.
- **Minimize External Dependencies:** Unfortunately, it is not practical (and sometimes not possible) to include external dependencies like `<script src="https://url.com/">` in a bookmarklet. Keep this in mind when writing your code.
- **Consider Code Length Limitations:** Some browsers may have limitations on the number of characters allowed in a bookmark. While I haven't personally encountered this, it's a good practice to minify or compress your code if you suspect it may exceed the character limit.

With these considerations in mind, you're ready to create your own bookmarklet! So let's get started with the examples below.

## Bookmarklet 1: QR Code Generator
This bookmarklet makes use of a free API, `https://api.qrserver.com`. It is a relatively simple code that generates a QR code for any page by going to the API link with the current page URL inputted into the `?data=` (data) parameter. Here is the code:

``` javascript
javascript:(function() {  var url = encodeURIComponent(window.location.href);  var qrCodeUrl = "https://api.qrserver.com/v1/create-qr-code/?data=" + url;  window.open(qrCodeUrl, "_blank");})();
```

As you can see, not too long. Most bookmarklets are relatively simple.

## Bookmarklet 2: Translate Page
This bookmarklet uses Google Translate to translate any page that you are on. When clicked, it prompts for the language (two-letter code, e.g., “French” → “fr”), and opens the translated page. Here is the code:
```javascript
javascript:(function() {  var lang = prompt("Enter language code to translate to:", "en");  var translationUrl = "https://translate.google.com/translate?sl=auto&tl=" + lang + "&u=" + encodeURIComponent(window.location.href);  window.open(translationUrl, "_blank");})();
```

## Bookmarklet 3: Dark Mode
This bookmarklet will turn a page into dark mode (or try to). It may break some pages.

![A picture is worth 1000 words.](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/xmrwwcx1s3uhn1g57hjx.png)

```javascript
javascript:(function() {  var style = document.createElement('style');  style.innerHTML = `    * {      color: white !important;      background-color: #111000 !important;    }  %60;  document.head.appendChild(style);})();
```

## Bookmarklet 4: Password Generator
This handy bookmark generates a random password. You are prompted for a length, and a password is generated. This bookmark especially makes use of the very convenient placeholder for browser APIs like prompts. 

```javascript
javascript:(function() {  function generatePassword(length) {    var charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-+={}|:"?#$*';    var password = '';    for (var i = 0; i < length; i++) {      var randomIndex = Math.floor(Math.random() * charset.length);      password += charset.charAt(randomIndex);    }    return password;  }  var passwordLength = prompt("Enter password length:", "8");  var generatedPassword = generatePassword(passwordLength);  prompt("Generated Password:", generatedPassword);})();
``` 
This one is a bit long, but it shouldn't cause any trouble.

## Bookmarklet 5: Email Copier
If you are like me and are paranoid about mistyping your email, this bookmarklet is right for you. Substitute `you@example.com` with your real email.

```javascript
javascript:(function() {  const email = "you@example.com";  const dummyElement = document.createElement("textarea");  document.body.appendChild(dummyElement);  dummyElement.value = email;  dummyElement.select();  document.execCommand("copy");  document.body.removeChild(dummyElement);})();
```
Personally, though this is one of the simpler ones, it is one of the most useful for me.

## Bookmarklet 6: Page Word Count
This bookmarklet was one of my first. Kind of boring, but I figured I might as well put it here. When you click the bookmark, it scans the page and tells you how many words are on it. Code:

```javascript
javascript:(function() {  var text = document.body.innerText || document.body.textContent;  var words = text.trim().split(/\s+/).length;  alert("Word Count: " + words);})();
```

## Bookmarklet 7: SEO Tips Bookmark
OK, not fully functional, but I put 20 SEO tips in it to get you started:

```javascript
javascript:(function() {  var pageUrl = window.location.href;  var tips = processDiagnosticData();  if (tips) {    alert('Page Diagnosis Tips:\n\n' + tips);  }  function processDiagnosticData() {    var tips = '';    var titleTag = document.querySelector('title');    if (!titleTag) {      tips += 'Title Tag is missing\n';    }    var metaDescriptionTag = document.querySelector('meta[name="description"]');    if (!metaDescriptionTag) {      tips += 'Meta Description is missing\n';    }    var headingTags = document.querySelectorAll('h1, h2, h3, h4, h5, h6');    if (headingTags.length === 0) {      tips += 'Heading Tags are missing\n';    }    var imgTags = document.querySelectorAll('img');    if (imgTags.length === 0) {      tips += 'Image Tags are missing\n';    }    var anchorTags = document.querySelectorAll('a');    if (anchorTags.length === 0) {      tips += 'Anchor Tags are missing\n';    }    var scriptTags = document.querySelectorAll('script');    if (scriptTags.length === 0) {      tips += 'Script Tags are missing\n';    }    var linkTags = document.querySelectorAll('link');    if (linkTags.length === 0) {      tips += 'Link Tags are missing\n';    }    var metaViewportTag = document.querySelector('meta[name="viewport"]');    if (!metaViewportTag) {      tips += 'Viewport Meta Tag is missing\n';    }    var canonicalTag = document.querySelector('link[rel="canonical"]');    if (!canonicalTag) {      tips += 'Canonical Tag is missing\n';    }    var robotsTag = document.querySelector('meta[name="robots"]');    if (!robotsTag) {      tips += 'Robots Meta Tag is missing\n';    }    var ogTags = document.querySelectorAll('meta[property^="og:"]');    if (ogTags.length === 0) {      tips += 'Open Graph Tags are missing\n';    }    var twitterTags = document.querySelectorAll('meta[name^="twitter:"]');    if (twitterTags.length === 0) {      tips += 'Twitter Card Tags are missing\n';    }    var altAttributes = document.querySelectorAll('img:not([alt])');    if (altAttributes.length > 0) {      tips += 'Alt Attributes are missing for some Images\n';    }    var formTags = document.querySelectorAll('form');    if (formTags.length === 0) {      tips += 'Form Tags are missing\n';    }    var inputTags = document.querySelectorAll('input');    if (inputTags.length === 0) {      tips += 'Input Tags are missing\n';    }    var textareaTags = document.querySelectorAll('textarea');    if (textareaTags.length === 0) {      tips += 'Textarea Tags are missing\n';    }    var buttonTags = document.querySelectorAll('button');    if (buttonTags.length === 0) {      tips += 'Button Tags are missing\n';    }    var tableTags = document.querySelectorAll('table');    if (tableTags.length === 0) {      tips += 'Table Tags are missing\n';    }    var metaCharsetTag = document.querySelector('meta[charset]');    if (!metaCharsetTag) {      tips += 'Charset Meta Tag is missing\n';    }    return tips;  }})();
```

Very much on the long side, but it will do okay.


## Bookmarklet 8: Element Highlighter
Basically, it changes the colors of all page elements, so you can see them:

![Image is worth 2000 words maybe?](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/onb0p6t1e5l722g2pgcy.png)

I really love this one as it can show me with just one click the layout of the page. So useful.

Here is the code:
```javascript
javascript:(function(){  function getRandomColor() {    var letters = "0123456789ABCDEF";    var color = "#";    for (var i = 0; i < 6; i++) {      color += letters[Math.floor(Math.random() * 16)];    }    return color;  }  function getContrastingColor(color) {    var hex = color.slice(1);    var r = parseInt(hex.substr(0, 2), 16);    var g = parseInt(hex.substr(2, 2), 16);    var b = parseInt(hex.substr(4, 2), 16);    var yiq = (r * 299 + g * 587 + b * 114) / 1000;    return yiq >= 128 ? "#000000" : "#FFFFFF";  }  function applyRandomStyle(element) {    var randomColor = getRandomColor();    element.style.backgroundColor = randomColor;    element.style.color = getContrastingColor(randomColor);  }  var elements = document.getElementsByTagName("*");  for (var i = 0; i < elements.length; i++) {    applyRandomStyle(elements[i]);  }})();
```
This one is certainly interesting for developers; it has helped me find problems with pages before.

## Bookmarklet 9: JSON Formatter
This bookmarklet formats JSON API responses:


### Before:

![sad](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jk3kaimcdl7qsed9fi10.png)

### After:


![extreme joy](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/mg3lmzru489vnrwgjfxy.png)


Incredibly useful if you do lots of API stuff like me.

Code:
```javascript
javascript:(function() { function syntaxHighlight(json) { json = JSON.stringify(json, undefined, 4); json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;'); return json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+-]?\d+)?)/g, function (match) { var cls = %27color: black;%27; if (/^"/.test(match)) { if (/:$/.test(match)) { cls = %27color: green;%27; } else { cls = %27color: darkorange;%27; } } else if (/true|false/.test(match)) { cls = %27color: red;%27; } else if (/null|-?\d+(?:\.\d*)?(?:[eE][+-]?\d+)?/.test(match)) { cls = %27color: purple;%27; } return %27<span style="%27 + cls + %27">%27 + match + %27</span>%27; }); } var contentType = document.contentType; if (contentType === "application/json") { var json = JSON.parse(document.body.innerText); var highlighted = syntaxHighlight(json); document.body.innerHTML = %27<pre>%27 + highlighted + %27</pre>%27; document.body.style.fontFamily = "Arial, sans-serif"; document.body.style.fontSize = "15px"; } else { alert("This page does not contain JSON."); }}());
```

Might actually be my favorite? Too hard to choose.

## Bookmarklet 10: Color Picker
Opens a color picker on any page so you can use it for your web dev stuff. Pretty simple.
```javascript
javascript:(function(){  var container = document.createElement('div');  container.style.position = 'fixed';  container.style.top = '10px';  container.style.right = '10px';  container.style.zIndex = '9999';  container.style.backgroundColor = 'white';  container.style.borderRadius = '10px';  container.style.padding = '10px';  container.style.boxShadow = '0 0 10px rgba(0, 0, 0, 0.3)';  container.style.display = 'flex';  container.style.alignItems = 'center';  var colorInput = document.createElement('input');  colorInput.type = 'color';  colorInput.style.width = '30px';  colorInput.style.height = '30px';  colorInput.style.marginRight = '10px';  var copyButton = document.createElement('button');  copyButton.textContent = 'Copy';  copyButton.style.padding = '5px 10px';  copyButton.style.marginRight = '10px';  copyButton.style.backgroundColor = '#4CAF50';  copyButton.style.color = 'white';  copyButton.style.border = 'none';  copyButton.style.borderRadius = '5px';  copyButton.style.cursor = 'pointer';  var closeButton = document.createElement('button');  closeButton.textContent = 'Close';  closeButton.style.padding = '5px 10px';  closeButton.style.backgroundColor = '#f44336';  closeButton.style.color = 'white';  closeButton.style.border = 'none';  closeButton.style.borderRadius = '5px';  closeButton.style.cursor = 'pointer';  copyButton.addEventListener('click', function() {    var color = colorInput.value;    var tempInput = document.createElement('input');    tempInput.value = color;    document.body.appendChild(tempInput);    tempInput.select();    document.execCommand('copy');    document.body.removeChild(tempInput);    alert('Color copied to clipboard: ' + color);  });  closeButton.addEventListener('click', function() {    container.remove();  });  container.appendChild(colorInput);  container.appendChild(copyButton);  container.appendChild(closeButton);  document.body.appendChild(container);})();
```

## Bookmarklet 11: Desktop Eyedropper
### Attribution: This was submitted by @aarvinr. Be sure to check him out!
This super handy bookmarklet lets you pick a color not just from the page, but from the whole desktop!

![color eyedropper bookmarklet](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/tvq4a8fp03la42nar23z.gif)


Check out it's GitHub repository here:
https://github.com/twogrey/CoPiBoo---Color-Picker-Bookmarklet

The demo is here:
https://twogrey.github.io/CoPiBoo---Color-Picker-Bookmarklet/
This doesn't work in some Linux distributions, but it works fine on Windows. 


## Bookmarklet 12: Restart Browser

Not a real bookmarklet, but cool, so I had to add it:

Only works in Chrome based browsers. Just make a bookmark with `chrome://restart/` as the URL. It will restart your browser when you click it.

## Bookmarklet 13: Page Performance Test

This bookmarklet performs a page performance test on the current page using Google PageSpeed Insights.


![page speed](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/tbf52z1bly9lujdaj0ql.png)


Code:

```javascript
javascript:window.location='https://developers.google.com/speed/pagespeed/insights/?url=%27+encodeURI(window.location);
```
Pretty simple, really.

## Bookmarklet 14: Ad Blocker

Removes ads from the current page.
Code:

```javascript
javascript:(function(){    /* Ad-B-Gone: Bookmarklet that removes obnoxious ads from pages */    var selectors = [    /* By ID: */    '#sidebar-wrap', '#advert', '#xrail', '#middle-article-advert-container',    '#sponsored-recommendations', '#around-the-web', '#sponsored-recommendations',    '#taboola-content', '#taboola-below-taboola-native-thumbnails', '#inarticle_wrapper_div',    '#rc-row-container', '#ads', '#at-share-dock', '#at4-share', '#at4-follow', '#right-ads-rail',    'div#ad-interstitial', 'div#advert-article', 'div#ac-lre-player-ph',    /* By Class: */    '.ad', '.avert', '.avert__wrapper', '.middle-banner-ad', '.advertisement',    '.GoogleActiveViewClass', '.advert', '.cns-ads-stage', '.teads-inread', '.ad-banner',    '.ad-anchored', '.js_shelf_ads', '.ad-slot', '.antenna', '.xrail-content',    '.advertisement__leaderboard', '.ad-leaderboard', '.trc_rbox_outer', '.ks-recommended',    '.article-da', 'div.sponsored-stories-component', 'div.addthis-smartlayers',    'div.article-adsponsor', 'div.signin-prompt', 'div.article-bumper', 'div.video-placeholder',    'div.top-ad-container', 'div.header-ad', 'div.ad-unit', 'div.demo-block', 'div.OUTBRAIN',    'div.ob-widget', 'div.nwsrm-wrapper', 'div.announcementBar', 'div.partner-resources-block',    'div.arrow-down', 'div.m-ad', 'div.story-interrupt', 'div.taboola-recommended',    'div.ad-cluster-container', 'div.ctx-sidebar', 'div.incognito-modal', '.OUTBRAIN', '.subscribe-button',    '.ads9', '.leaderboards', '.GoogleActiveViewElement', '.mpu-container', '.ad-300x600', '.tf-ad-block',    '.sidebar-ads-holder-top', '.ads-one', '.FullPageModal__scroller',    '.content-ads-holder', '.widget-area', '.social-buttons', '.ac-player-ph',    /* Other: */    'script', 'iframe', 'video', 'aside#sponsored-recommendations', 'aside[role="banner"]', 'aside',    'amp-ad', 'span[id^=ad_is_]', 'div[class*="indianapolis-optin"]', 'div[id^=google_ads_iframe]',    'div[data-google-query-id]', 'section[data-response]', 'ins.adsbygoogle', 'div[data-google-query-id]',    'div[data-test-id="fullPageSignupModal"]', 'div[data-test-id="giftWrap"]' ];    for(let i in selectors) {        let nodesList = document.querySelectorAll(selectors[i]);        for(let i = 0; i < nodesList.length; i++) {            let el = nodesList[i];            if(el && el.parentNode)                el.parentNode.removeChild(el);        }    }})();
```

It works surprisingly well!

## Bookmarklet 15: Site Technology Profiler
### Attribuition: This was subitted be @opensourcee. Be sure to check him out! 

This utilizes a site called w3techs to analyze a URL and determine it's technologies. 

Code:
```javascript
javascript:(function() {
  var currentSite = window.location.hostname;
  var redirectUrl = "https://w3techs.com/sites/info/" + currentSite;
  window.location.href = redirectUrl;
})();
```

![for above text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ox3ckl2s3fcg4o8yme3n.png)



## Goodbye for now! 
I hope you have enjoyed learning about bookmarklets. In the comments below, share some of your own! I might add them (with attribution, of course).

Oh, and be sure to check out my other posts on DEV, and my portfolio site that I made recently, too! 

[https://the-best-codes.github.io/](https://the-best-codes.github.io/?ref=dev.to_post&click=https://dev.to/best_codes/11-amazing-bookmarklets-for-web-devs-what-are-they-anyways--3pk6/&site=https://dev.to/&reason=best-codes-simple-free-website-post)

## More Bookmarklets: [https://the-best-codes.github.io/tools/bookmarks/](https://the-best-codes.github.io/tools/bookmarks/?ref=dev.to&site=dev.to&reason=post_bookmarklet&click=https://dev.to/best_codes/11-amazing-bookmarklets-for-web-devs-what-are-they-anyways--3pk6/edit)

Thanks for reading, and happy coding!