Category: Developer
· URL: /tools/base64-checker-online.html
Input (Base64/Base64URL or plain text for encoding)
Output (result)
Tip: for JWT, each segment is usually
Base64URL and may omit padding.
Privacy: runs locally in your browser. No uploads, no tracking scripts.
How to use
Paste your string, then choose what you want to do.
- Paste Base64/Base64URL into the input box.
- Click Validate to check characters, length, and padding (missing padding is handled).
- Click Decode to decode to text; if it’s binary, you’ll get a hex preview.
- To encode, type plain text and click Encode, then optionally switch to Base64URL / remove padding.
Keywords this page targets (natural cluster): base64 checker online, validate base64 string, base64url checker, check base64 padding, fix base64 padding, base64 decoder online, base64 encoder online, decode base64 to text, encode text to base64, is this base64 valid, base64 validator, base64url decode, convert base64url to base64, base64 string checker, base64 decode without padding, online base64 validation, base64 decode to utf-8, base64 invalid character check, add missing base64 padding, remove base64 whitespace
Secondary intents covered: Verify whether an input string is valid Base64 or Base64URL, Auto-normalize input by removing whitespace and fixing missing padding, Decode Base64 to UTF-8 text when possible, Encode plain text to Base64 or Base64URL, Identify common Base64 issues (invalid characters, bad padding, wrong length), Convert Base64URL to standard Base64 and vice versa, Copy results quickly for debugging or API testing, Inspect binary outputs via hex when decoded data is not valid UTF-8, Troubleshoot JWT segments and other Base64URL payloads
FAQ
What’s the difference between Base64 and Base64URL?
Base64 uses + and /, while Base64URL uses - and _ to be URL-safe; Base64URL often omits = padding.
Is missing padding '=' always an error?
No. Many Base64URL strings omit padding; this tool treats missing padding as OK when it can be safely restored.
Why does decoding sometimes show “Binary data (not valid UTF-8)”?
Base64 can represent arbitrary bytes. If the decoded bytes aren’t valid UTF-8 text, the tool shows a hex preview instead.
Does this tool send my data to a server?
No. Validation/encoding/decoding runs locally in your browser.
Why is “mixed Base64 and Base64URL characters” invalid?
Using +// together with -/_ usually indicates a corrupted or incorrectly transformed string.
Can it handle whitespace and newlines in Base64?
Yes. The tool removes whitespace before validating/decoding, which is common for PEM blocks or wrapped output.
How do I convert Base64URL to standard Base64?
Run Validate to see the normalized standard Base64, or decode then re-encode without Base64URL output.