Everything you need to know about TwentyOneTools. Can't find your answer? Search below or browse by category.
Completely safe. TwentyOneTools processes all files entirely within your browser using JavaScript and WebAssembly. Your files are never uploaded to any server — they never leave your device. We have no access to your files, and nothing is stored, logged, or transmitted anywhere.
No. Every conversion happens locally in your browser. We have no servers processing your files. This means you can even use TwentyOneTools offline once the page has loaded, and sensitive documents like contracts or medical records stay completely private.
Yes — in fact, TwentyOneTools is one of the safest options available precisely because nothing is uploaded. Many competing tools send your files to remote servers, creating privacy risks. With TwentyOneTools, your files stay on your device from start to finish, making it suitable for legal documents, financial records, medical files, and anything else you wouldn't want leaving your computer.
We don't collect any personal data or file content. We may use basic anonymous analytics (such as page views) to understand how the site is used, but this contains no personally identifiable information and never includes your files or their contents.
It's three simple steps: (1) Select your input format from the "Convert from" dropdown. (2) Select your desired output format from the "Convert to" dropdown. (3) Drop your file into the upload zone or click "Choose file" to browse. The conversion happens instantly and your file downloads automatically.
Yes, completely free. There are no subscriptions, no hidden fees, and no credit card required. No account creation is needed either — just visit the site and start converting.
No account, no sign-up, no email required. Open the site, convert your file, download the result. That's it.
The current limit is 100 MB per file. Since all processing happens in your browser, very large files may be slower to convert depending on your device's processing power and available memory. For best performance on large files, we recommend using a desktop or laptop rather than a mobile device.
There are no limits. Convert as many files as you like, as often as you like. Because everything runs in your browser and we have no servers involved, there's nothing to throttle or restrict.
Yes. TwentyOneTools works on any device with a modern browser — iPhone, Android, tablet, desktop, or laptop. No app download is required. Simply open the site in your browser and convert away. Note that very large files may convert more slowly on mobile due to limited processing power.
Once the page has fully loaded in your browser, many conversions will work without an internet connection since all processing is local. However, you'll need an initial internet connection to load the page and its libraries. We recommend loading the page while connected, then you can convert files even if your connection drops.
It depends on the formats involved. Converting to a lossless format (like PNG, WAV, or FLAC) preserves full quality. Converting to a lossy format (like JPG or MP3) will apply compression, which can reduce file size but may slightly reduce quality — this is inherent to those formats. We use high-quality settings to minimise any degradation. Converting from a lossy format to another lossy format (e.g. JPG to WEBP) will involve one additional compression step.
The output resolution will always match the input. If your converted image looks low quality, it's likely because the original file was already low resolution. Conversion cannot add detail that wasn't in the original — only AI upscalers can do that. If you're converting to JPG, the format uses lossy compression which may introduce subtle artefacts on very detailed images.
For simple documents, formatting is largely preserved. However, complex layouts with custom fonts, tables, columns, or embedded images may not translate perfectly when converting between formats — especially when converting to plain text (TXT) or Markdown (MD). For the most faithful result, converting to PDF or HTML will retain more of the original structure than plain text formats.
TwentyOneTools supports a wide range of formats across five categories: Images (JPG, PNG, WEBP, GIF, BMP, TIFF, SVG, ICO), Documents (PDF, DOCX, DOC, TXT, RTF, HTML, MD), Audio (MP3, WAV, OGG, FLAC, AAC, M4A, AIFF), Video (MP4, WEBM, MOV, AVI, MKV), and Data (CSV, JSON, XML, XLSX, YAML). See our full formats page for details on each.
Greyed-out options are formats that are not compatible with your selected input. For example, you can't convert an audio file to an image — it doesn't make logical sense. The converter automatically disables incompatible targets to save you time and avoid errors.
HEIC support in browsers is limited — Apple's HEIC format is not natively decodable in most browsers outside of Safari on Apple devices. If you're on a Mac or iPhone using Safari, HEIC conversion should work. On Windows or Android, we recommend first converting HEIC to JPG using your phone's built-in share settings (most iPhones offer this automatically when sharing to non-Apple apps).
Video conversion runs using your browser's built-in MediaRecorder API, which is most reliable in Chrome and Edge. Firefox and Safari have more limited support. For best results with video conversion, we recommend using the latest version of Google Chrome. Very long videos may also take significant time to process since they're rendered frame by frame in the browser.
Try these steps: (1) Refresh the page and try again. (2) Make sure you're using a modern browser — Chrome, Firefox, Edge, or Safari. Older browsers may lack support for certain conversion features. (3) Check that your file isn't corrupted by opening it in another application first. (4) If your file is very large, try a smaller test file to confirm the format is supported. (5) For video or audio issues, try switching to Chrome which has the broadest codec support.
Since conversions happen entirely in your browser, large files use your device's CPU and RAM. This is normal — the page may be unresponsive briefly while processing. For best performance: close other browser tabs, avoid very large files on low-powered devices, and use a desktop or laptop for demanding conversions like video or high-resolution images.
Your browser may be blocking automatic downloads. Check for a download prompt in your browser's address bar or notification area. In Chrome, you may need to allow "automatic downloads" for this site in your browser settings. You can also try clicking the "Download again" button that appears after a successful conversion.
TwentyOneTools works best on the latest versions of Google Chrome, Microsoft Edge, Mozilla Firefox, and Apple Safari. Chrome and Edge offer the broadest format support, particularly for video conversion. Internet Explorer is not supported. We recommend keeping your browser up to date for the best experience.