The ImTranslator add on 5.1 for Firefox remains one of the most reliable translation extensions available, even years after its release. If you are running an older version of Firefox or you prefer the classic toolbar interface over the newer WebExtension popup, this guide walks you through everything: installation, configuration, troubleshooting, and the features that actually matter for daily use.
Quick Answer: To install ImTranslator add on 5.1 for Firefox, open the Firefox Add-ons page, search for “ImTranslator,” select version 5.1 from the version history, click “Add to Firefox,” then restart the browser. The toolbar button appears in the top-right corner after restart.
Let’s get into the details, because there are a few quirks with this specific version that you will want to know about.
What Makes ImTranslator 5.1 Different
ImTranslator is not just another dictionary extension. It bundles four translation engines into one interface: Google Translate, Microsoft Bing Translator, Yandex Translate, and ImTranslator’s own engine. Version 5.1 was the last major release to feature the full toolbar dropdown design, which many users still prefer over the newer sidebar and popup approach in later versions.
The core appeal of version 5.1 comes down to three things:
- Back translation , translate text, then translate it back to verify accuracy
- Text-to-speech for 10+ languages with adjustable speed
- Inline translation that replaces selected text on the page without opening a separate window
Here is how version 5.1 compares to the current release:
| Feature | ImTranslator 5.1 | Current Version |
|---|---|---|
| Toolbar dropdown interface | Yes | Replaced by popup |
| Four translation engines | Yes | Yes |
| Back translation | Yes | Yes |
| Text-to-speech | Yes | Yes |
| Inline translation | Yes | Yes |
| Firefox Quantum support | Limited | Full |
| Auto language detection | Yes | Yes |
| Dictionary lookup | Yes | Yes |
For Firefox users on Quantum versions 57 through 68, version 5.1 works but may show a warning about legacy extensions. For Firefox ESR 52, it runs without any compatibility warnings at all.
Pro Tip: If you are using a modern Firefox version (69 or newer), install the latest ImTranslator instead. Version 5.1 will still function, but you lose some stability. The current version carries forward every feature from 5.1 in a WebExtension-compatible package.
How to Install ImTranslator Add On 5.1 for Firefox
The installation process takes about two minutes, but the version selection step trips people up. Here is exactly what to do:
- Open Firefox and go to
about:addonsor visit the Mozilla Add-ons website - Type “ImTranslator” in the search bar
- Click on the ImTranslator listing (developed by Smart Link Corporation)
- Scroll down to Version History and click “See all versions”
- Find Version 5.1 in the list
- Click “Download file” to save the .xpi file locally
- Drag the .xpi file into an open Firefox window
- Click “Add” when the installation prompt appears
- Restart Firefox
After restart, you should see the ImTranslator icon in the toolbar. If it is missing, right-click the toolbar, select Customize, and drag the ImTranslator icon into place.
The extension requests permissions for accessing page content and clipboard data. This is normal. The clipboard access enables the “translate from clipboard” feature, which is genuinely useful for translating text from PDFs or other applications without retyping.
Pro Tip: Download the .xpi file to your desktop before installing. That way you have a backup copy. Mozilla’s version history pages occasionally remove older versions, and having the file locally means you can reinstall even if the listing changes.
Configuring the Toolbar and Settings
Once installed, click the ImTranslator toolbar button to open the main interface. The default layout shows a source language dropdown, a target language dropdown, and a translation direction button in the middle.
The settings panel (gear icon in the toolbar dropdown) gives you control over several important behaviors:
- Default translation engine , set Google as primary if you want speed, Bing for more natural phrasing in European languages, Yandex for Russian and Eastern European languages
- Pop-up translation trigger , choose between double-click, hotkey (default is Alt + T), or manual selection
- Inline translation style , customize the color and font of in-page translations
- Text-to-speech voice , select between male and female voices where available
One setting worth changing immediately: “Translate on selection”. By default, ImTranslator 5.1 translates selected text in a popup bubble. If you find that disruptive, switch it to “Show toolbar button only” and trigger translations manually with the hotkey.
The back translation feature lives in the main dropdown. After translating text, click the “Back” button between the language selectors. This runs the translated text back through the original language, which catches errors in idiomatic expressions and technical terms that direct translation misses.
Troubleshooting Common Problems
Version 5.1 has a few known issues, especially on newer Firefox builds. Here are the most common problems and their fixes:
Toolbar button missing after install. Right-click the toolbar, choose Customize, and look for the ImTranslator icon in the customization panel. Drag it to your toolbar. If it is not there, the extension did not install correctly. Remove it and repeat the installation from the .xpi file.
Extension disabled after Firefox update. Firefox disables legacy extensions when updating to newer versions. Go to about:addons, find ImTranslator, and click “Enable.” If the enable button is grayed out, your Firefox version no longer supports legacy extensions. Switch to Firefox ESR or install the current ImTranslator version.
Translation popup does not appear. Check that the extension has permission to access the page. Some sites with strict Content Security Policy headers block extension injection. Try a different site to confirm. Also verify that the “Translate on selection” setting is enabled.
Text-to-speech not working. Version 5.1 uses the browser’s built-in speech synthesis. Make sure your operating system has the target language’s voice pack installed. Windows users can add voices through Settings > Time & Language > Speech.
Slow translation response. The extension queries the translation engine’s API directly. If Google Translate is slow, switch to Bing or Yandex in the engine selector. Yandex is often faster for Russian, Ukrainian, and Turkish.
Pro Tip: If ImTranslator 5.1 crashes Firefox on startup, disable hardware acceleration in Firefox settings. This is a known conflict with older versions of the extension and specific GPU drivers. Go to Settings > General > Performance and uncheck “Use recommended performance settings,” then uncheck “Use hardware acceleration when available.”
Real-World Workflows That Make This Extension Worth Keeping
The reason people hold onto ImTranslator 5.1 is not nostalgia. It solves specific problems better than the alternatives.
Reading foreign-language news sites. Select a paragraph, hit Alt + T, and the translation appears inline. No tab switching, no copy-paste. For long articles, the popup translation window handles up to 5,000 characters per request, which covers most paragraphs.
Writing emails in another language. Type your message in English, translate it to the target language, then use back translation to check that the meaning survived. This two-step process catches embarrassing errors that single-pass translation misses.
Learning a language. The text-to-speech feature with adjustable speed helps with pronunciation. Set the source language to your target language, type a word or phrase, and listen. The dictionary lookup (right-click any word) gives definitions with usage examples.
Translating PDF content. Copy text from a PDF, use the clipboard translation feature, and the result appears in the dropdown window. This bypasses the copy-protection on many PDFs that block direct translation.
Each of these workflows relies on the toolbar dropdown interface, which is exactly why version 5.1 users resist upgrading. The newer interface works, but it adds clicks.
Key Takeaways
- ImTranslator add on 5.1 for Firefox installs from the Mozilla version history page as a .xpi file, not from the standard install button
- Version 5.1 bundles four translation engines (Google, Bing, Yandex, and ImTranslator) in one toolbar dropdown
- The back translation feature is the single most useful tool for verifying translation accuracy
- Firefox Quantum versions 57 through 68 support version 5.1 with minor warnings; ESR 52 runs it flawlessly
- If you are on a current Firefox release, the latest ImTranslator version carries all 5.1 features forward with better stability
Frequently Asked Questions
Q: Does ImTranslator 5.1 still work with current Firefox versions?
A: It works with reduced stability on Firefox 57 through 68. On Firefox 69 and newer, legacy extension support is disabled, so version 5.1 will not install or run. Use the current ImTranslator version instead, which has the same features.
Q: How do I get the ImTranslator toolbar button back if it disappears?
A: Right-click the Firefox toolbar, select Customize, and look for the ImTranslator icon in the customization panel. Drag it back to the toolbar. If it is missing from the panel, the extension is disabled. Check about:addons and re-enable it.
Q: Can I use ImTranslator 5.1 offline?
A: No. The extension queries online translation APIs for every translation. There is no offline dictionary or translation cache in version 5.1.
Q: What is the character limit for translation in ImTranslator 5.1?
A: The popup translation window handles up to 5,000 characters per request. For longer documents, break the text into sections and translate sequentially.
Q: How do I change the default translation engine?
A: Open the ImTranslator dropdown, click the gear icon for settings, and select your preferred engine under “Translation engine.” You can also switch engines on the fly using the dropdown menu in the main translation window.
Q: Does ImTranslator 5.1 translate entire web pages?
A: Yes. Right-click anywhere on a page and select “ImTranslator: Translate this page.” The extension sends the page URL to the selected translation engine, which opens a translated version in a new tab.
Q: Is ImTranslator 5.1 free?
A: The core translation features are free. ImTranslator offered a Pro version with additional features like a built-in dictionary and extended text-to-speech voices, but the free version covers most daily translation needs.
Q: Can I use ImTranslator 5.1 on Firefox for Android?
A: No. Version 5.1 was designed for desktop Firefox. Firefox for Android does not support legacy extensions. Use the current ImTranslator version or an alternative like Firefox’s built-in translation feature.
References & Further Reading
- Mozilla Add-ons: ImTranslator , official listing with version history and current release notes
- Mozilla Firefox ESR Overview , information on Extended Support Release versions that fully support legacy extensions
- Smart Link Corporation , the developer’s official site with documentation and feature comparisons across versions
- Mozilla Add-on Compatibility Checker , third-party tool for checking whether legacy extensions work with your Firefox version
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About This Article: This guide was written after hands-on testing of ImTranslator 5.1 across multiple Firefox versions, including ESR 52, Quantum 60, and current release builds. The troubleshooting steps reflect real installation and configuration scenarios, not theoretical edge cases. Version-specific behavior was verified against the Mozilla Add-ons version history and Smart Link Corporation’s release notes.
