Base64 Encode
Paste any text below to instantly encode it as a Base64 string. The opposite operation is also generated at once, below.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Base64 Encode
SGVsbG8sIFdvcmxkISBUaGlzIGlzIGEgQmFzZTY0IGVuY29kaW5nIGV4YW1wbGUu
Input size
48 bytes
Output size
64 bytes
Byte-size comparison
Both directions
SGVsbG8sIFdvcmxkISBUaGlzIGlzIGEgQmFzZTY0IGVuY29kaW5nIGV4YW1wbGUu
Invalid Base64 input — it must contain only the letters A–Z/a–z, digits 0–9, '+', '/', and end with the correct '=' padding, with a total length that's a multiple of 4.
About These Parameters
- Text / Base64 string
- The single input field drives both directions at once — if it's plain text, the Base64 Encode card shows the meaningful result; if it's a valid Base64 string, the Base64 Decode card does. It can be a word, a sentence, or a full document.
- Mode
- Each card shows one direction — Encode or Decode — applied to the same input. Click a card's name to open its dedicated page, prefilled with an example for that direction.
How Base64 Encoding Works
From Bytes to 6-Bit Groups
Base64 encoding takes the raw bytes of the input (each byte is 8 bits) and regroups them into
chunks of 6 bits. Each 6-bit chunk can represent a value from 0 to 63, which maps directly to
one of the 64 characters in the Base64 alphabet: 26 uppercase letters, 26 lowercase letters,
10 digits, and two symbols (+ and /). Because 3 bytes (24 bits) split
evenly into exactly 4 six-bit groups, Base64-encoded output is always about 33% longer than
the original data.
Why the "=" Padding?
When the input length isn't a multiple of 3 bytes, the last group is padded with zero bits and
one or two = characters are appended so the decoder knows exactly how many of the
final 6-bit groups are "real" data versus padding. A single trailing = means the
last group represented 2 original bytes; == means it represented just 1.
Where Base64 Is Used
Base64 was originally designed for MIME email attachments, which needed a way to send binary
files (images, documents) through mail systems that only guaranteed safe delivery of plain
ASCII text. Today it's used the same way for embedding small images directly in CSS/HTML as
data: URIs, encoding binary data in JSON payloads and JWT tokens, and storing
binary blobs in text-only fields like environment variables.
Base64 Is Not Encryption
Base64 provides no confidentiality — anyone can decode it back to the original data instantly, with no key or password required, using this tool or any Base64 decoder. It only changes the representation of the data (so it's safe to transmit as text), never its content, and should never be relied on to hide sensitive information such as passwords or personal data.
Frequently Asked Questions
Why is Base64 output longer than the input?
Because 3 bytes of input become 4 characters of output (each character carries only 6 of its 8 bits of useful information), Base64 text is roughly 33% larger than the original binary data, plus up to two padding characters.
Is Base64 the same as encryption?
No. Base64 is a reversible encoding, not encryption — it has no secret key, and anyone can decode it back to the original data. Use a real encryption algorithm (e.g. AES) if you need to keep data confidential.
Why did decoding my text fail?
Valid Base64 only contains the characters A–Z, a–z, 0–9, "+", "/", and "=" padding, with a total length that's a multiple of 4 after whitespace is removed. If your input is ordinary text rather than a Base64 string, decoding it will fail — that's expected.