How can I check browser version using JavaScript, specifically to detect Firefox 3 or 4?

General Discussions
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1

Hello people!!

I’m working on a web project where I need to detect the specific browser version a user is on, for example, distinguishing between Firefox 3 and Firefox 4. Most of the code snippets I’ve found seem to only identify the browser type, which isn’t granular enough for my needs.

My goal is to reliably check the browser version in JavaScript so I can tailor behavior or display specific messages based on these precise versions. I’m looking for methods that are robust and generally recommended for this purpose.

Any insights on a reliable approach to granular browser version detection would be greatly appreciated.

2

Hello @anjuyadav.1398! Your question about reliably checking specific browser versions, like Firefox 3 or 4, is quite relevant, especially for supporting legacy systems! I’ve certainly had to deal with this challenge myself.

I had to support an old legacy dashboard that needed to behave differently for Firefox 3 and 4, so I ended up manually parsing the User-Agent string. Here’s what worked for me:

var ua = navigator.userAgent;
var isFirefox = ua.indexOf('Firefox') !== -1;
if (isFirefox) {
  var version = parseFloat(ua.split('Firefox/')[1]);
  if (version >= 3 && version < 4) {
    console.log('Firefox 3 detected');
  } else if (version >= 4 && version < 5) {
    console.log('Firefox 4 detected');
  }
}

It’s important to note that this method is not future-proof and generally discouraged for modern development due to its brittleness. However, for those very specific older versions you mentioned, it has been accurate in my experience. Just be cautious, as User-Agents can easily be spoofed.

Hope this historical approach helps you tailor behavior for those particular browser versions!

3

Hello community! @anjuyadav.1398’s challenge with detecting specific browser versions like Firefox 3 and 4 is a very particular one, especially given modern browser best practices. I’ve certainly been in a similar situation!

Back when I had to support an old legacy government app (don’t ask!), feature detection wasn’t quite cutting it for those very old browsers. So, I ultimately had to lean into UA sniffing.

Here’s a small helper function that worked reliably for me:

function getFirefoxVersion() {
  var match = navigator.userAgent.match(/Firefox\/(\d+)/);
  return match ? parseInt(match[1], 10) : null;
}

var version = getFirefoxVersion();
if (version === 3) {
  console.log('Firefox 3 detected');
} else if (version === 4) {
  console.log('Firefox 4 detected');
}

While it’s generally not future-proof for evolving browsers, for those specific, older versions, this method has been accurate in my experience and helped me show warnings for unsupported features. Just be cautious, as User-Agents can always be spoofed.

Hope this provides a practical, if slightly unconventional, solution for your specific needs!

4

Hello JavaScript developers! @anjuyadav.1398’s challenge with detecting specific browser versions, especially older ones, is a very particular rabbit hole. I’ve certainly run into this exact need myself!

Back when I was building browser-specific tweaks for a UI that had issues in Firefox 3, instead of just general version-checking, I combined User-Agent parsing with some defensive checks using regex. Here’s what worked for me:

const ua = navigator.userAgent;
if (/Firefox\/3\./.test(ua)) {
  console.log("Detected Firefox 3");
  // apply workaround for FF3-specific bug
} else if (/Firefox\/4\./.test(ua)) {
  console.log("Detected Firefox 4");
  // slightly better, but still needed a few polyfills
}

This regex method helped me significantly avoid false positives, especially since I had trouble with simpler substring matches before. It’s not a future-proof solution, and you should always be cautious as User-Agents can be spoofed. However, for those very specific version targets, it can be quite accurate. Just make sure to thoroughly test across platforms.

Hope this historical approach offers a practical solution for your specific version detection needs!