Base64エンコーダー / デコードr
エンコード text to Base64 or decode Base64 back to text. Supports Unicode and URL-safe. 無料, in-browser.
What is Base64 encoding?
Base64 is a binary-to-text encoding scheme that represents binary data using only 64 printable ASCII 文字: A–Z, a–z, 0–9, +, and /. Because those 文字 survive almost any transport layer, Base64 is everywhere: email attachments (MIME), data URLs in HTML, JWTs, CSS embedded fonts, and API authentication tokens. Encoding transforms data so it can be sent in a text-only context; decoding restores the original bytes exactly.
This free Base64 encoder handles both directions plus one extra: URL-safe encoding, which swaps + and / for - and _ and drops the padding, producing strings that are safe inside URLs and query parameters. Unicode text is fully supported — emoji, accented letters, and CJK 文字 are encoded via UTF-8. Everything runs in your browser, so nothing you encode ever leaves your device.
使い方 use the Base64 encoder
- Paste text or a Base64 string into the box.
- Click エンコード to turn text into Base64, デコード to turn Base64 back into text, or URL-safe for a URL-friendly encoded variant.
- コピー the result with one click — malformed Base64 input shows a clear error instead of garbage output.
Frequently asked questions
What is a Base64 encoder?
A Base64 encoder converts text or binary data into a string of 64 safe ASCII 文字, so it can be stored or transmitted in text-only systems such as emails, URLs, and JSON payloads.
Does it support Unicode?
Yes — Unicode text is converted to UTF-8 bytes before encoding, so emoji, accented letters, and non-Latin scripts like Chinese or Arabic are encoded and decoded correctly.
What is URL-safe Base64?
Standard Base64 contains + and /, which are not safe in URLs. URL-safe Base64 replaces them with - and _ and removes padding, so the encoded string works as-is in links and query parameters.
How do I decode Base64 back to text?
Paste the Base64 string and click デコード. The tool converts each 4-character group back to its original bytes and shows the decoded text. Invalid input is reported with a clear error.