Html Validator

Name: Html Validator
Rating: 4.2308 (26 reviews)
Author: Marc Gueury

HTML Validator is a Mozilla extension that adds HTML validation inside Firefox, Mozilla. The number of errors of a HTML page is seen on the form of an icon For Firefox 56, use 0.974 (see all versions below). For Firefox 57, see Web Extensions.

Download

Install

Features & Capabilities

HTML Validator is a powerful Mozilla Firefox extension that integrates HTML validation directly into your browsing experience. It displays the number of HTML errors through an icon in the status bar or inside the Developer Tools tab, helping web developers quickly identify and address issues.

Built using the trusted Tidy and OpenSP (SGML Parser) algorithms originally developed by the W3C, the extension validates HTML locally without sharing data with third-party servers. It supports validation of server-sent HTML as well as dynamic content after Ajax calls. The latest versions provide comprehensive support for HTML5 and accessibility checks aligned with WAI standards. Now available as a Web Extension compatible with Firefox 57+ and Chrome, HTML Validator is a multilingual tool available in 17 languages with ongoing community support.

User Growth & Download Statistics

Add-on Developer Tools

By:

Daily users:

Rating:

Version:

0.9.9.5 Last updated: 2021-08-04

Version code:

5275583

Creation date:

2004-09-11

Risk:

Permissions:

Content scripts matches:

<all_urls>

Size:

2.65MB

URLs:

Website

Full description:

Source:

Firefox Add-ons Store

Data ingested on:

2026-06-15

Compare stats and ranking:

Ranking

# 1,020 ▼ 5

Other rankings

#107 in Web Development ▼ 1

#151 in Other extensions ▼ 1

#1 in html keyword 40

#23 in algorithm keyword 3

#24 in x data keyword 11

Upgrade to see more rankings

For Developers

Monetize with App Pass Boost with Extension Booster

Contact the developer

Chrome-Stats does not own this Firefox add-on. Please use these information below to contact the Firefox add-on developer.

Developed by:

Marc Gueury

Firefox Add-ons Store

https://addons.mozilla.org/firefox/addon/html-validator/

Website:

https://www.gueury.com/mozilla/

User Reviews

Users find the Html Validator add-on valuable for catching HTML errors and improving code quality. However, several common issues include loss of support for CSS validation, false warnings in offline mode, broken frame validation, reduced functionality in recent Firefox versions, and less user-friendly access to validation results. Despite these drawbacks, it remains a useful tool for those serious about HTML coding.

Pros

Helps users catch HTML errors effectively while browsing or coding, improving code quality.
Long-standing and reliable tool appreciated by users serious about writing clean HTML.
Provides validation results directly within the browser, integrating well with developer workflows.

Cons

No longer supports CSS HTML Validator, limiting its validation capabilities.
Offline validation can cause false warnings, such as incorrect missing tags.
Validation of frames and certain HTML elements is broken or no longer possible in recent Firefox versions.
Options and compatibility issues with newer Firefox versions and Chrome cause partial functionality or failure.
Requires extra clicks to access validation results and lacks immediate visual indicators, reducing usability.

Recent reviews

by 远离*****, 2025-03-27

by 远离*****, 2025-02-13

this add is good

by Fi*****, 2024-07-02

View all user reviews ›

Is Html Validator Safe?

Risk impact

Risk impact measures the level of extra permissions an extension has access to. A low risk impact extension cannot do much harms, whereas a high risk impact extension can do a lot of damage like stealing your password, bypassing your security settings, and accessing your personal data. High risk impact extensions are not necessarily malicious. However, if they do turn malicious, they can be very harmful.

Html Validator requires some sensitive permissions that could impact your browser and data security. Exercise caution before installing.

Risk impact analysis details

Critical Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
High ****** ********* ** * ****** ******** ******** ********** * ******* ******* *****
High ******* ******* **** *** ****** ***** *** ***** ** ******* **** ********* ********* ** * *********** *****
High ****** ******* *** ********* ********* ******** ***** *** ** ********** ****** * ******** ******* *****
Medium ****** ** ********* ****** ********* *** **** ****** **** **** ** ******* ** ********** **** ***********

Risk likelihood

Risk likelihood measures the probability that a Firefox add-on may turn malicious. This is determined by the publisher and the Firefox add-on reputation on Firefox Add-ons Store, the amount of time the Firefox add-on has been around, and other signals about the Firefox add-on. Our algorithms are not perfect, and are subject to change as we discover new ways to detect malicious extensions. We recommend that you always exercise caution when installing a Firefox add-on.

Html Validator has earned a fairly good reputation and likely can be trusted.

Risk likelihood analysis details

High This extension has low user count. Unpopular extensions may not be stable or safe.
Low **** ********* *** ******* **** **** * ****** **** ***** ******** *** **** ****** ** ** ****** *** *****
Low **** ********* *** ***** **** **** * ****** **** ***** ********** *** **** ****** ** ** ****** *** *****
Good **** ********* *** **** **** *******