Developer & data utilities
Base64 encode / decode
Encode or decode text and small payloads.
Run Base64 encode / decode online
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Base64 encoding converts binary data (files, images, binary strings) into a printable ASCII text format. This is essential in web development and data transmission contexts where binary data needs to be safely embedded in text-based formats such as JSON, XML, HTML, email bodies (MIME), or URLs.
Base64 decoding reverses this process — converting a Base64-encoded string back to its original binary or text form. Common use cases include decoding JWT tokens (JSON Web Tokens), decoding Base64-encoded API responses, extracting embedded images from data URIs, and decoding encoded email attachments.
Developers encounter Base64 constantly: data URIs for embedding small images in CSS/HTML (data:image/png;base64,...), API authentication tokens, encoding binary payloads for REST APIs that only accept JSON, and email attachment encoding (MIME). This tool provides quick encode/decode without leaving the browser.
How to use this utility
- Use the controls below—paste text, pick files, or adjust options as described on the tool.
- Click the main action button. Processing runs in your browser on this device.
- Download or copy the output. Check the processing note for any external services used by this operation.
Common use cases
- Decoding a Base64-encoded JWT token to inspect its payload for debugging.
- Encoding a binary file or image to Base64 for embedding in a JSON API payload.
- Decoding a Base64 string in an API response to extract the original data.
- Extracting an embedded Base64 image from a data URI for saving as an image file.
- Encoding API credentials (client_id:client_secret) to Base64 for an HTTP Basic Auth header.
Tips for best results
- 1Base64 output is approximately 33% larger than the original input — factor this in if you're using Base64 encoding for size-sensitive transmissions.
- 2For URL-safe Base64 (used in JWT and some APIs), use the URL-safe variant ('+' → '-', '/' → '_', no padding '=') instead of standard Base64.
- 3Trailing '=' or '==' in Base64 strings are padding characters — they're required for proper decoding and should not be stripped unless the system you're sending to explicitly handles unpadded Base64.
- 4If a decoded Base64 string contains garbage characters, the encoded string may have used a different character encoding — try UTF-8 vs ISO-8859-1 decoding.
- 5For debugging JWT tokens, only the payload section (middle segment between two dots) needs to be Base64-decoded.
Frequently asked questions
- Is Konnect2Tools free?
- Yes. These in-browser tools are completely free to use with no account required for core functionality.
- Do my files leave my device?
- Browser document operations run locally, except where the operation uses an external service, such as AI summarisation. Read the processing note before using sensitive inputs.
- Is the Base64 encode / decode tool safe to use?
- Local operations process document content on your device. External-service operations may send inputs as described in the processing note. Keep originals and inspect the output.
- What is Base64 used for in web development?
- Base64 is used for encoding binary data in text contexts: embedding small images directly in HTML/CSS via data URIs, encoding file uploads in JSON API bodies, MIME encoding for email attachments, HTTP Basic authentication headers, and JWT token payloads.
- Is Base64 a form of encryption?
- No — Base64 is encoding, not encryption. It is fully reversible without any key. Anyone can decode a Base64 string to its original content. Do not use Base64 for security or confidentiality — use proper encryption for sensitive data.
- What is the difference between standard Base64 and URL-safe Base64?
- Standard Base64 uses '+' and '/' characters, which have special meanings in URLs. URL-safe Base64 replaces '+' with '-' and '/' with '_' so the encoded string can be included in a URL or query parameter without percent-encoding.
- Why does my Base64 string end with '=' or '=='?
- These are padding characters that make the Base64 string length a multiple of 4. They're a normal part of the encoding, not an error. Some implementations strip padding; others require it — match the expectations of the system you're sending to.
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