Base64 is not encryption, but most converters still upload what you give them — and people paste tokens far more often than they realise.
| Capability | jsonversal | base64.guru & similar | Command line (base64) |
|---|---|---|---|
| Data leaves the browser | Never | Usually yes | N/A — local |
| URL-safe variant | Yes | Varies | Flag needed |
| Decode detects bad input | Yes | Varies | Yes |
| Binary files | Yes | Varies | Yes |
| No signup | Yes | Yes | Yes |
| Available offline | Yes after first load | No | Yes |
Base64 is encoding, not encryption — anyone decoding the output can read it. That is exactly why the upload matters: a Basic-Auth header or an API key pasted into a converter should not become someone else's server log. Use the shell tool for automation, a browser converter when you need it by hand.