Base64 encode & decode

Choose encode or decode and paste your data. Changing how you view the result never changes the operation itself.

Local · no upload · encoding is not encryption

Advanced: format conversion / validation

Format conversion requires different formats. For padding or letter-case cleanup within the same format, use Validate / normalize. The tool will not wrap the data in another encoding layer.

Current operationEncode

UTF-8 text → Base64 encode

Display: auto / stacked / side-by-side

Layout

Narrow screens stay stacked. If the page looks tiny on mobile, check your browser’s desktop-site setting; this option does not change browser zoom.

Run operation

Input data type

Source text

Input limit: 1 MiB. Source text is not cleaned automatically. Use a file to preserve exact line breaks and binary content.

Processing settings

Advanced: encoded whitespace & limits

Ignore ASCII spaces, tabs, and line breaks in Base64 / Hex

Strict validation by default; alphabets are not mixed. Encoded-text limit: 4 Mi UTF-16 units; result limit: 4 MiB; timeout: 10 seconds.

Ctrl / ⌘ + Enter to run

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Result view

Finish an operation before switching the result view.

Not processed yet

Result preview

What is the difference between the two downloads?

Encoded text is the current UTF-8 / Base64 / Hex view. The result file contains the actual bytes and does not change when you switch views; the filename indicates the format.

Base64URL view options

Keep Base64URL = padding in this view

This changes only how the result is displayed; it does not change the operation above.

Processing rules, data integrity & privacy

Encoding accepts source text or files; decoding accepts Base64 / Base64URL. To add another encoding layer, explicitly encode the representation as source text.
Format conversion requires different formats; use the dedicated validation / normalization mode for the same format. Alphabets cannot be mixed; invalid padding and non-zero pad bits are rejected. Hex does not accept 0x prefixes or arbitrary separators.
UTF-8 decoding is strict and preserves BOM. Non-text results can be viewed as Hex or downloaded. Text areas may normalize line breaks, so use files for exact round trips.
Input limit: 1 MiB; result limit: 4 MiB; encoded text is additionally limited to 4 Mi UTF-16 units. Decompression checks size incrementally and returns no partial result on overflow. Peak browser memory cannot be fully bounded. Tasks time out after 10 seconds and can be cancelled.
Preview shows up to 65,536 UTF-16 units; copy and download still use the complete result. Switching views does not rerun the operation; editing source data or operation settings disables stale results.
Clearing or replacing with a sample requires confirmation and cannot be undone. Data is processed only in this page’s memory and Worker; it is not uploaded, written to URLs or persistent storage, or executed as HTML. Results are released when you leave, so keep your own backup.

Base64 encode & decode

1Run operation

2Review completed result

Run operation

Review completed result