Base64 Encoder and Decoder Tool

Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable characters. Originally defined in RFC 2045 (MIME specification), it was later standardized in RFC 4648. Its core idea is to convert binary data that cannot be directly transmitted in text protocols into pure ASCII text for safe transmission.

The Base64 encoding process can be summarized as "three bytes become four characters": each group of 3 bytes (24 bits) of binary data is split into 4 six-bit fragments, and each fragment serves as an index to look up the corresponding character from the character table. The character table includes 26 uppercase letters (A-Z), 26 lowercase letters (a-z), 10 digits (0-9), plus + and /.

Since 4/3 ≈ 1.33, the encoded data size increases by approximately 33%. This size expansion is its main disadvantage, but it is acceptable in most scenarios. If the original data is not a multiple of 3, zeros are padded at the end and filled with = characters.

Common use cases include: image embedding in web pages (Data URI), API data transfer, email attachments, configuration file storage, etc. This tool supports bidirectional encoding and decoding of text and images to meet various development needs.

URL-Safe Base64. The + and / used in standard Base64 have special meanings in URLs (+ represents space, / represents path separator), so a safe variant is needed. URL-safe Base64 replaces + with -, / with _, and typically omits the trailing = padding characters. This tool supports conversion between both formats.

Encoding failure troubleshooting: Chinese text encoding requires UTF-8 encoding. The browser's native btoa() function only supports Latin-1, so Chinese characters need to be transcoded via encodeURIComponent first. This tool automatically handles these issues.

Decoding failure troubleshooting: Check if the Base64 string is complete and does not contain line breaks or whitespace characters. Some systems wrap Base64 at 76 characters per line, which needs to be removed before decoding. Also, confirm whether standard or URL-safe format is used—mixing them will cause failure.

Image preview failure troubleshooting: Confirm the input is valid image Base64 data. If it doesn't contain a Data URI prefix (e.g., data:image/png;base64,), you can check the "Add image prefix" option. If preview still fails, the image data may be corrupted or the format may not be supported.

All Base64 encoding/decoding operations are performed locally in the browser and no data is uploaded to the server. The text you input, images you upload, and generated Base64 strings are all processed entirely on your device, protecting your data privacy.

Important: Base64 is not an encryption algorithm. Anyone can easily decode Base64 strings to obtain the original data, so never use it to protect sensitive information. If you need to encrypt data, use professional encryption tools such as AES, RSA, SM2/SM4, etc.

Safe usage recommendations: For Base64 data containing highly sensitive information (such as production environment keys, unencrypted user data), it is recommended to perform data anonymization before using this tool. Although the tool does not upload data, caution is always the right choice.

If you need true encryption protection for your data, we provide a complete set of encryption tools, including symmetric encryption (AES, SM4), asymmetric encryption (RSA, SM2), hash algorithms (MD5, SHA, SM3), etc. All tools support local processing.