Ever seen a weird-looking string like aGVsbG8= in an API response, a data URL, or a CTF challenge? It's most likely Base64. So what is it, and how do you decode it?
What is Base64?
Base64 is an encoding that represents binary or text data using only 64 safe characters (A–Z, a–z, 0–9, +, /). It is not encryption — anyone can decode it. Its purpose is to let data pass safely through text-based channels (email, JSON, URLs). For example, it's used to embed an image in HTML as data:image/png;base64,....
Where you'll run into it
- Embedded data in APIs/JSON
- Email attachments, data URLs
- "Hidden" (but not encrypted) text in CTF challenges
Base64 encode/decode in the browser
👉 swapfile.io Base64 encode & decode — encode text to Base64 or decode it back, instantly, entirely in your browser, with nothing uploaded. Unicode characters are handled correctly.
To identify more encodings or ciphers, the cipher & encoding identifier comes in handy.
In short
Base64 is an encoding for transport, not encryption — those strings ending in = are usually it. To quickly decode or generate one, use the in-browser Base64 tool. Private and instant.