Instantly encode plain text to Base64 or decode Base64 strings back to readable text. Private, client-side processing.
Base64 appears in email attachments, data URIs for inline images, HTTP Basic Authentication headers, JSON Web Tokens, API keys, and XML payloads. Thumbnail Download's Base64 tool lets you encode or decode any text instantly in your browser — no data is sent to any server.
Type or paste your input and output appears instantly. The Swap button flips input and output and switches mode in one click — handy for verifying a round-trip encode-decode cycle.
Base64 converts binary data into printable ASCII characters — A–Z, a–z, 0–9, plus (+) and slash (/), with equals (=) for padding. Because these characters are safe in text-based systems, Base64 became standard for embedding binary data in text protocols. The encoding produces output approximately 33% larger than the original.
Base64 is not encryption. It is fully reversible — anyone with the encoded string can decode it instantly. Never use Base64 as a security measure. Use it only for safe transport of binary data in text contexts, combined with proper encryption where security is required.