What Base64 is and why it exists

Base64 is a way to represent arbitrary binary data — an image, a PDF, a cryptographic key — as plain ASCII text. The 8-bit-per-byte source is regrouped into 6-bit chunks; each 6-bit value (0–63) maps to one of 64 printable characters (A-Z, a-z, 0-9, +, /), with = as padding. The result is roughly 33% larger than the original, but it survives any text-only transport: email bodies (MIME's original use case), JSON payloads, URLs (with - and _ swapped in for + and /), CSS url(data:…) embeds, JWT segments, and SMTP attachments.

Base64 is not encryption — it's a reversible encoding. Anyone with the encoded string can decode it. Use it for transport-safety, not secrecy.

What this tool does

• Text ↔ Base64, UTF-8 safe (handles emoji, CJK, accented characters correctly).
• File ↔ Base64, with automatic MIME type detection so you can paste the output straight into an <img src="data:image/png;base64,…"> or a CSS background-image: url(data:…) embed.
• Base64 → file download for decoded binaries — paste a chunk you saw in an API response, get the underlying PDF/image back.
• URL-safe variant (- for +, _ for /, no padding) — the form JWTs and signed URLs use.
• All processing in your browser. No uploads. Safe for sensitive payloads (API keys, JWTs, certificates).

Common use cases

• Embed an image in HTML/CSS without a separate request. Tiny icons (under ~5 KB) often perform better inlined.
• Decode the payload of a JWT to inspect claims. Each JWT segment is URL-safe Base64.
• Inspect a data: URL you found in scraped HTML — extract the original image.
• Send binary data through a JSON API that only accepts strings.
• Reconstruct a file from an email or log that has it Base64-encoded.
• Generate a fingerprint of a binary you can compare across systems (combined with the Hash tool).