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What Is Base64 Encoding?
Base64 is a binary-to-text encoding scheme that represents binary data using only 64 printable ASCII characters: A–Z, a–z, 0–9, plus sign (+), and forward slash (/). The equals sign (=) is used as padding. Because it only uses safe ASCII characters, Base64 is the standard way to transmit binary or special-character data through systems that can only handle plain text.
The most common use is HTTP Basic Authentication, where the username:password pair is Base64-encoded before being placed in the Authorization header. Despite the name, this is encoding — not encryption. Anyone who has the encoded string can decode it instantly, which is why HTTPS is still required when using Basic Auth.
Base64 also appears in JWT tokens (the header and payload sections are Base64url-encoded), email attachments (MIME encoding), embedding small images in CSS or HTML as data URLs, and storing binary data in JSON or XML formats that do not support raw bytes.
- HTTP Basic Auth: Authorization: Basic base64(username:password)
- JWT tokens: header and payload sections are Base64url-encoded
- Email attachments: MIME uses Base64 to encode binary files as text
- Data URIs: images embedded in HTML/CSS as base64-encoded strings
- API payloads: binary data in JSON or XML fields
How to Use This Base64 Encoder Decoder
To encode: paste or type your plain text into the input area and click Encode. The Base64 output appears instantly and can be copied with one click. To decode: paste a Base64 string and click Decode to see the original plain text. If the input is not valid Base64, the tool shows an error message rather than producing garbage output.
This tool handles standard Base64 as defined in RFC 4648. If you are working with JWT tokens or URL-safe Base64, note that those use a slightly different alphabet (- and _ instead of + and /) and may omit the padding = characters. Most Base64 decoders handle this variation automatically.
Base64 vs Base64url — What Is the Difference?
Standard Base64 uses + and / as the 62nd and 63rd characters. These are not safe in URLs because + can be interpreted as a space and / is a path separator. Base64url solves this by replacing + with - and / with _ and removing trailing = padding. This is the variant used in JWT tokens, OAuth state parameters, and URL-safe file identifiers.
For decoding JWT tokens, the standard Base64 decoder in this tool may need you to replace - with + and _ with / first, or use a dedicated JWT decoder tool.
- Standard Base64: uses + and / characters, safe for files and headers
- Base64url: uses - and _ characters, safe for URLs and JWT tokens
- Padding: standard uses trailing = characters; Base64url often omits them
Security Note: Base64 Is Encoding, Not Encryption
A Base64 string looks like random gibberish but it offers zero security. Anyone can decode it in seconds. Never use Base64 to obscure sensitive data like passwords or personal information. For real security, use encryption (AES, RSA) and store credentials in secret managers rather than encoding them in client-side code or URLs.
Why marketers use this tool
- Encode any text to Base64 without a terminal or code
- Decode Base64 payloads from API responses and JWT tokens instantly
- Runs entirely in the browser — no data is sent to any server
Frequently Asked Questions
What is Base64 encoding used for?
Base64 is used to encode binary data as ASCII text so it can be transmitted through systems that only handle plain text. Common uses include HTTP Basic Authentication headers, JWT token payloads, email attachments (MIME), data URIs for images, and API payloads that carry binary data in JSON or XML fields.
Is Base64 the same as encryption?
No. Base64 is encoding, not encryption. Anyone with the encoded string can decode it instantly. It only converts binary data to text-safe characters. For security, use proper encryption algorithms like AES-256 and store secrets in a secret manager, not in Base64-encoded strings in your code.
Can I decode a JWT token with this tool?
Partially. A JWT token has three parts separated by dots: header, payload, and signature. The header and payload are Base64url-encoded, so you can decode them here by replacing - with + and _ with /. For a full JWT breakdown with signature verification, use the dedicated JWT decoder tool.
Why does my decoded output look like gibberish?
Base64 can encode any binary data, not just text. If the original data was an image, PDF, or other binary file, decoding it as text will produce unreadable output. Base64 text decoding only works cleanly when the original data was plain text.
What is the = padding at the end of Base64 strings?
Base64 encodes data in groups of 3 bytes into 4 characters. When the input length is not a multiple of 3, padding = characters are added to make the output length a multiple of 4. One = means one byte of padding; == means two bytes of padding.