8+ best Firefox Developer add-ons in 2021!

Firefox is considered to be one of the most widely used browsers worldwide. It’s fast, efficient, and offers great privacy and security for users. Many users prefer to use Firefox Above Google Chrome. i also use Firefox more often than Chrome because of its speed and other features that make my job easier.

Firefox offers several features that can be helpful for everyone in any group. Whether students, teachers or developers, Firefox has something in store for everyone. However, when it doesn’t have all of the functionality in its browser, it allows users to take advantage of those features in the form of add-ons.

As a developer myself, I find it difficult to cope with all of my tasks at once. From coding to clearing the cookies so the browser doesn’t get stuck, the list is endless. Although not all of these functions can be managed at once Firefoxwho have favourited add-ons do a pretty good job of helping me.

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I was having a hard time finding the best add-ons for me. But after a lot of research, I’ve made a list of the best add-ons that I think will be helpful to you as a developer. Let’s have a look!


HTML validator

Are you looking for an add-on to help you spot errors in your HTML codes, then have you come to the right place? HTML Validator does just that for you.

It shows you all the mistakes so you can get your job done twice as fast.

Some of the well-known functions of HTML Validator are:

  • It helps validate the HTML you currently have or someone sent it.
  • You can see the errors clearly and correct them from now on.
  • The correction takes place entirely on your server.
  • No third-party apps or websites have access to your data.
  • It can be translated into 17 different languages.

However, troubleshooting problems can sometimes arise as it might be necessary to identify all of the errors at once and you might have to wait.

Download the HTML validator


Are you someone who is constantly struggling with your codes and their sources? Well, with the Octotree Firefox Add-On, you don’t have to keep hitting GitHub to look for your codes.

All things can now be done with a single click. Octotree can be useful to programmers all over the world.

Some of the most important aspects of Octotree are:

  • It improves the way you code.
  • You have access to the choice of font and design of the code.
  • You can manage multiple tabs for your codes.
  • You can also choose the font for your file icons.
  • This allows you to manage multiple GitHub accounts.

Although it comes with great features, only a part of them can be accessed in the free version. Most of its functions are only available in the pro or paid version.

Download Octotree

Page performance test

If you are always worried that your web pages are loading slowly or are easily irritated by it, the Page Performance Test will help you to calm down. It gives you all the necessary data on website speed and loading time.

You can also save all of this data for future reference or comparison.

Page performance test Firefox Browser add-on

To name just a few of the amazing features of the Page Performance Test add-on:

  • It measures the performance and speed of a website using web APIs.
  • You can save these for later.
  • It’s extremely easy to install and get up and running.
  • It gives you an accurate picture of page load time and statistics.

However, it can take you some time to get the results, which can be irritating if you are in a hurry.

Request page performance test

User ap

If you use screenshots every day and comment on them for various purposes, Usersnap will become your preferred add-on from now on. It helps you take screenshots and comment on them as you wish.

This add-on has helped me a lot when I need to attach a screenshot to an article.

Screenshot from Usersnap Firefox Add to

Some of the most important functions of Usersnap are:

  • You can take screenshots of websites and mark them up.
  • You can also add comments or feedback in screenshots.
  • It also allows you to file a bug report.
  • It comes with a 14-day trial period.

While it is almost perfect in all of its features, it is a paid service and not everyone can afford it. The test phase also ends after just 14 days.

Download user app

User-agent toggle switch

This is extremely efficient Firefox Add-on as it allows you to switch the user agent of your browser. All of this can be achieved very easily.

Even if you are not a techie, you can easily use this add-on for your work.

User agent switcher and manager Firefox Add to

Some of the notable features of User-Agent Switcher are:

  • You can access websites that you didn’t have before.
  • Not all websites will ask for a subscription when you change the user agent.
  • You can also use a new language for the user-agent switch.
  • You can also report a bug or problem that needs to be fixed.

However, it may not work on certain websites and cause problems. This can cause inconvenience for you later.

Get the user-agent switcher


Ghostery is one of those add-ons that not only keeps you safe from distractions but also protects your privacy. It helps to let you know about trackers.

You can disable the trackers that can steal your data or sneak into your private information.

How to enable privacy and security in Firefox Computer?

Ghostery privacy blocker Firefox Add to

Ghostery is packed with so many great features. Some of them are:

  • It blocks any unnecessary data or ads.
  • You can also view or block trackers.
  • It loads a page faster and optimizes page performance.
  • All your data is marked as anonymous for more privacy.

Despite having so many features, it still had its drawbacks. This add-on may have access to much of your information, which could result in data loss or threats to your privacy.

Download Ghostery


If you’ve been looking for a color picker for a long time, your search ends here. With Colorzilla you can choose any color of your choice for the browser window.

It also allows you to have a suitable color for any image you want.

ColorZillla color selection as Firefox Add on

Some of the fantastic features of Colorzilla are:

  • It has an eyedropper that allows you to have any color for a window.
  • It has an advanced color picker that is similar to Photoshop’s.
  • You can view your most recently selected colors in the gradient.
  • They also have a website color analyzer.

However, once you select the paint, the paint may not apply and it may take some time to do so. It can be a little annoying.

Download Colorzilla

Cookie manager

If you want to delete or simply edit your cookies, Cookie Manager Firefox Add-on will do it for you. It helps you to display, add or change the cookies.

You also have the option of importing or exporting your cookies for various purposes.

How to clear history, cookies and cache in Firefox Computer?

Cookie manager Firefox renewal

Many of the great features of Cookie Manager are:

  • You can enable or disable the add-on as you wish.
  • You can add, edit or delete cookies.
  • You can recognize and delete the same set of cookies with one click.
  • You can import or export cookies.
  • You can also put cookies on the whitelist.

The Cookie Manager extension can be a problem if you are browsing in private mode Firefox. This is a serious problem and needs to be addressed.

Download cookie manager

HTTPS everywhere

If you are always worried about the data breach, the HTTPS Everywhere add-on will assure you about the same for a lifetime. It encrypts your web no matter where you go or what you search.

Any website that supports HTTPS will be automatically encrypted as soon as you use this add-on.

HTTPS Everywhere add-on for safe surfing on Firefox

To name just a few of the most important features of HTTPS Everywhere:

  • It encrypts your data when you visit a website.
  • It works automatically on websites using HTTPS.
  • Unlike others, it is easy to use.
  • It rewrites all HTTPS requests.

However, it can consume a lot of memory and cause problems on your computer Firefox Browser. It can start to lag and slow down.

Download HTTPS anywhere

Conclusion: best Firefox Developer add-ons

Mozilla Firefox has been the favorite browser of many people around the world including me. It has so many brilliant features to offer and it also tends to work better than the other browsers. Trusted by millions of people Firefox as the default browser and keep using it for a variety of purposes.

It has been of great help to people from all walks of life. It’s no secret that the add-ons offer more than enough for the features that are Firefox is missing. These add-ons are like a boon for developers who have a lot to accomplish in a short amount of time. From now on we have compiled this list of add-ons for their use and help. With the advantages and disadvantages mentioned above, I am sure that you will make a wise choice.

These add-ons helped me a lot too. As a developer, the Octotree add-on helps me with coding. Ghostery, on the other hand, offers me a distraction-free environment to work. I am so glad I discovered these add-ons.

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Which is your favorite Firefox Add-on from the above list? Would you like to add more that you consider to be the best?

Finally, here are the recommended web browsers for your computer and mobile phone that you should try.

windowMac OSiOSAndroidLinux
Chrome windowChrome MacChrome iOSChrome AndroidFirefox Linux
Firefox windowSafari MacSafari iOSEdge AndroidChrome Linux
Edge windowFirefox MacEdge iOSSamsung internetEdge Linux

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