File Converter Privacy Comparison: Who Uploads Your Files?
Not all file converters handle your data the same way. Some upload files to remote servers. Others process everything locally. This comparison shows exactly how 26 popular file converters work, so you can make an informed choice.
Methodology: Data sourced from each service's privacy policy, FAQ pages, and public documentation as of March 2026. "Browser" means files are processed entirely in your browser with no server upload. "Server" means files are uploaded to the provider's servers for processing. "Local" means desktop software you install.
Three Types of File Converters
Browser-Based (Client-Side)
Files never leave your device. Processing happens in your browser using JavaScript or WebAssembly. You can verify this by checking the Network tab in browser DevTools during conversion.
Privacy risk: Lowest
Server-Based (Cloud)
Files are uploaded to the provider's servers, processed remotely, and returned to you. Your data passes through third-party infrastructure. Reputable services encrypt and delete files, but you must trust their policies.
Privacy risk: Moderate
Installable Software
Desktop applications you download and install. Files stay on your computer, but you must trust the installer itself. The FBI specifically warned about malicious converter installers in 2025.
Privacy risk: Low (if trusted source)
Comparison Table
| Service | Processing | Uploads Files? | Signup? | Data Retention | Free Limit | Open Source? | Tools |
|---|---|---|---|---|---|---|---|
| FileToolWorks | Browser | No | No | None | None | No | 40+ |
| VERT.sh | Browser | No | No | None | None | Yes | ~20 |
| FileForge | Browser | No | No | None | None | Yes | ~40 |
| SafeConvert | Browser | No | No | None | None | No | ~30 |
| OfflineConvert | Browser | No | No | None | None | No | ~30 |
| ezyZip | Browser | No | No | None | None | No | ~50 |
| Convertio | Server | Yes | Free tier available | 24 hours | 100 MB (free) | No | 300+ |
| CloudConvert | Server | Yes | Free tier available | After processing | 1 GB | No | 200+ |
| Zamzar | Server | Yes | Free tier available | 24 hours (free) | 50 MB (free) | No | 100+ |
| SmallPDF | Server | Yes | Free tier (2/day) | 1 hour | 5 GB | No | 20+ |
| iLovePDF | Server | Yes | Free tier available | 2 hours | Varies by tool | No | 25+ |
| FreeConvert | Server | Yes | Free tier available | A few hours | 1 GB (free) | No | 100+ |
| PDF24 | Server | Yes | No | A few hours | Varies | No | 30+ |
| Adobe Acrobat Online | Server | Yes | Required for some | After processing | 100 MB | No | 20+ |
| Online-Convert | Server | Yes | Free tier available | 24 hours | 100 MB (free) | No | 100+ |
| FastlyConvert | Hybrid | Partial | No | After processing | Varies | No | ~30 |
| SaferPDF | Browser | No | No | None | None | No | PDF only |
| HandBrake | Local (install) | No | No | None | None | Yes | Video only |
| Stirling PDF | Local (self-host) | No | No | None | None | Yes | PDF only |
| FFmpeg | Local (install) | No | No | None | None | Yes | Audio/Video |
| PDFsam | Local (install) | No | No | None | None | Yes | PDF only |
| NoFileUpload | Browser | No | No | None | None | No | ~10 |
| NoUploadConvert | Browser | No | No | None | None | No | ~15 |
| LocalConverter | Browser | No | No | None | None | No | ~20 |
| FreeConverter.cloud | Browser | No | No | None | None | No | ~20 |
| NoUploadTools | Browser | No | No | None | None | No | ~10 |
How to Verify Any Converter's Privacy Claims
You do not need to trust what any file converter says about privacy. You can verify it yourself in under 60 seconds:
- Open the converter website in Chrome, Firefox, or Edge
- Press F12 to open Developer Tools
- Click the Network tab
- Upload and convert a small test file
- Watch the Network tab. If your file data appears in any outgoing request, the converter uploads to a server. If the only requests are for page assets (HTML, CSS, JS, WASM modules), it processes locally.
Browser-based converters like audio compressors and PDF mergers that use WebAssembly will download a WASM module on first use, but your actual file data stays in the browser tab.
The FBI Warning: What Happened
In March 2025, the FBI Denver Field Office issued a warning about free online file converter tools being used to distribute malware. The malicious converters functioned as expected (converting .doc to .pdf, for example) but secretly installed ransomware, credential stealers, or crypto miners on users' devices.
The FBI specifically warned about converters that required downloads or installations, as well as those that uploaded files to unknown servers where personal data could be scraped.
Browser-based converters avoid both attack vectors. There is nothing to install (the tool runs in your existing browser tab), and files never leave your device. For a deeper breakdown, see our security explanation or the full FBI warning analysis.
When Server-Based Converters Make Sense
Server-based converters are not inherently dangerous. Reputable services like CloudConvert (ISO 27001 certified) and SmallPDF (encrypted transfer, 1-hour retention) have legitimate security practices. Server processing makes sense when:
- You need to convert rare or complex formats that require specialized server software
- File sizes are very large and your device lacks the processing power
- You need batch processing of hundreds of files with an API
For common conversions (image format changes, PDF merging, audio compression, video trimming), browser-based tools handle these well without any server involvement.
Try Browser-Based Conversion
All of these tools process files in your browser. No upload, no signup, no file size limits:
Quick Safety Checklist
Before using any file converter, check these five things:
- 1.Does it upload your files? Open DevTools (F12), click Network, and convert a test file. No outgoing data = safe.
- 2.Does it require a download or install? The FBI warned about malicious converter installers. Browser-based tools need no install.
- 3.Does it require signup or email? Legitimate browser-based converters do not need your personal information.
- 4.Does the URL match the official site? Scam converters use URLs similar to real tools. Check for misspellings or extra words in the domain name.
- 5.Does it use HTTPS? A padlock icon in the address bar means the connection is encrypted. Avoid any converter on plain HTTP.
Frequently Asked Questions
Are free online file converters safe to use?
It depends on how they process your files. Browser-based converters that process files locally in your device are the safest option because your data never leaves your computer. Server-based converters upload your files to remote servers, which introduces privacy risks. The FBI warned in 2025 about malicious file converter sites distributing malware. You can verify safety by opening DevTools (F12) and watching the Network tab during conversion.
Which file converters do not upload your files?
Browser-based converters like FileToolWorks, VERT.sh, SafeConvert, OfflineConvert, ezyZip, FileForge, NoFileUpload, NoUploadConvert, and LocalConverter process files entirely in your browser using JavaScript or WebAssembly. Your files never leave your device. You can verify this by checking the Network tab in browser DevTools during conversion.
What did the FBI say about file converters?
In March 2025, the FBI Denver Field Office warned about free online file converters being used to distribute malware. The malicious converters appeared to work normally but secretly installed ransomware, credential stealers, or crypto miners. The FBI warned specifically about converters that required downloads or installations, and those uploading files to unknown servers.
How can I tell if a file converter uploads my files?
Open the converter in your browser, press F12 to open DevTools, click the Network tab, then upload and convert a test file. If your file data appears in any outgoing request, the converter uploads to a server. If the only requests are for page assets (HTML, CSS, JS, WASM modules), it processes everything locally in your browser.
Are browser-based file converters safer than server-based ones?
Yes, browser-based converters are safer for privacy because your files never leave your device. Server-based converters upload your data to third-party servers where it could potentially be accessed, stored, or intercepted. However, reputable server-based services like CloudConvert (ISO 27001 certified) have legitimate security practices and make sense for rare formats or very large files.
What is the difference between browser-based and server-based file converters?
Browser-based converters use JavaScript or WebAssembly to process files directly in your browser tab. Your files stay on your device. Server-based converters upload your files to remote servers for processing, then return the converted file. Browser-based tools offer better privacy but may be slower for very large files. Server-based tools can handle more formats but require trusting the provider with your data.
About This Comparison
This page compares 26 file converter services based on publicly available information from their websites, privacy policies, and documentation. Last updated March 2026. Policies may change. We recommend checking each service's current privacy policy before use.
FileToolWorks is included in this comparison. We built this page to help users make informed decisions about file converter privacy, regardless of which service they choose. If you find any inaccuracies, please let us know.