Decode Base64 to JSON
Paste a base64 or base64url string that encodes JSON. The tool decodes the bytes as UTF-8, parses the JSON, and pretty-prints it so you can read what is inside.
When JSON hides in base64
Base64 turns arbitrary bytes into ASCII so they survive URLs, headers, and cookies. JWT payloads, OAuth state, and many config blobs are just JSON that was base64-encoded. Decode the string and you get the original object back.
Standard vs URL-safe
This tool accepts both alphabets. Standard base64 uses + and /; the URL-safe variant used in JWTs swaps them for - and _ and often drops the = padding. Either works — it normalizes before decoding.
What it does not do
It decodes and parses; it does not verify signatures. If you are inspecting a JWT, the payload is readable by anyone — never trust it without checking the signature server-side. For header + payload together, use the decode-JWT tool.
FAQ
I get 'Not valid base64'. Why?
The string has characters outside the base64 alphabet, or it was truncated. Copy the full token and remove any surrounding quotes or whitespace.
It decoded but says invalid JSON.
The base64 decoded to something that is not JSON — maybe an image or plain text. Base64 is just a byte encoding; not every base64 string contains JSON.
Does it handle URL-safe base64?
Yes. Base64url with - and _ and missing padding is normalized automatically before decoding.