Base64 Decode
Decode Base64 strings to plain text — paste, decode, and copy instantly.
Decoded text will appear here...About Base64 Decode
Base64 Decode is a free online tool that converts Base64-encoded strings back into their original readable text. Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable ASCII characters. You will encounter it in JWT payloads, HTTP Basic Auth headers, data URIs embedded in CSS or HTML, MIME email attachments, and API responses that wrap binary content for safe transport over text-based protocols.
The most common reason to need a decoder is inspection: you receive an opaque Base64 string in a log file, an HTTP header, or a configuration value and you need to see what is actually inside it. This tool gives you the plain text in one click so you can verify a JWT claim, check an encoded credential, or confirm that a data URI contains what you expect. It handles the full Base64 alphabet including the standard characters A–Z, a–z, 0–9, +, and /, plus the = padding characters.
Every decoding operation runs entirely in your browser using the native atob() function combined with a TextDecoder, which correctly reconstructs multi-byte UTF-8 characters. No data leaves your device, there is no account required, and there is no usage limit — making it safe to paste tokens, credentials, or any sensitive encoded payload you need to inspect.
Key Features
UTF-8 safe decoding
Uses atob() paired with TextDecoder so multi-byte characters — accented letters, CJK text, emojis — are reconstructed correctly rather than becoming garbled mojibake.
100% client-side
Decoding runs in your browser only. Nothing is uploaded to a server, so you can safely paste JWTs, API keys, or any encoded secrets.
Clear error messages
Invalid padding, illegal characters, and corrupted strings all produce a specific error message so you know exactly what is wrong with the input.
Monospace split-pane view
Input and output sit side by side in a fixed-height code editor layout, making it easy to compare the encoded string with its decoded result.
One-click copy
Copy the decoded text to your clipboard instantly with a single button, ready to paste into your terminal, code editor, or document.
No size limits
Because processing is local, you can decode large payloads — long JWTs, encoded file blobs, or multiline data URIs — without hitting any server-side restrictions.
How to Use
Paste Base64
Paste your Base64-encoded string into the input pane.
Decode
Click "Decode" to convert the Base64 string back to readable text.
Copy Result
Use the copy button to grab your decoded text.
Example
A Base64 string is fed into the decoder and the original UTF-8 text is recovered in the output pane.
SGVsbG8sIFdvcmxkIQ==Hello, World!Common Use Cases
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Inspecting JWT payloads
The middle segment of a JSON Web Token is a Base64url-encoded JSON object. Paste it here to read the claims — user ID, expiry, roles — without needing a dedicated JWT library or debugger.
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Decoding HTTP Basic Auth headers
HTTP Basic Auth encodes credentials as Base64 in the Authorization header. Decode the value to verify which username and password are being sent during debugging or integration testing.
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Reading embedded data URIs
Data URIs in CSS or HTML encode images and fonts as Base64. Decode the payload to confirm the file type prefix or check that the data is not truncated before embedding it.
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Decoding API response fields
Some REST and GraphQL APIs return binary content — thumbnails, PDFs, certificates — as Base64 fields. Decode them to read metadata or confirm the content before writing it to disk.
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Verifying configuration values
Kubernetes secrets, CI environment variables, and cloud config stores often Base64-encode sensitive values. Decode them to confirm the correct value was set without running a full pipeline.