Base64 Decode
Found a long jumble of letters and digits ending in = signs? It is probably Base64. Paste it here to see the text inside.
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What it does
Put Base64 into the Base64 box and the decoded text shows up in the Text box. The decoder is relaxed about formatting: it skips line breaks and spaces, does not mind if the = padding is missing, and handles the URL-safe variety that swaps + and / for - and _ without you needing to say so. For example, V2VsbCBkb25lIQ== decodes to Well done!
Base64 can carry any kind of data, not just words. If the output is full of replacement symbols (�), the string most likely holds a picture, a document or some other file rather than text, and the box can only display text. The boxes are linked, so typing in the Text box encodes instead, and each box has its own copy button alongside a Clear button. Decoding happens in the browser, so nothing is uploaded.
How to use it
- Copy the Base64 string and paste it into the Base64 box.
- Read the decoded text in the Text box.
- If you see a length warning, check that no characters went missing when you copied.
- Press Copy text to use the result, or Clear to start over.
More tips
- Use the encoder to make a Base64 'secret' for a lesson, then show how instantly anyone can reverse it.
Ideas for the classroom and home learning
- KS3 (11–14)Hide a short starter question in Base64 on the board; the first pupils to decode it on the tool read it to the class.
- KS3 (11–14)Online safety: show that Base64 'looks' secret but is not, and discuss why real security needs proper encryption.
- KS4 (14–16)Give a valid and a broken string; learners explain why a string whose length is one more than a multiple of four can never be valid.
- KS4 (14–16)Compare standard and URL-safe Base64 and discuss why certain symbols cause problems in web addresses.
Questions
What text is SGk= ?
Hi. Try pasting it to see for yourself.
What does a length warning mean?
Valid Base64 never ends with a single leftover character once you count it in fours. One was probably dropped while copying.
Do I need to tell it the string is URL-safe?
No. Both standard and URL-safe Base64 are recognised automatically.
Does my text leave my computer?
No, decoding stays on your device. Even so, Base64 protects nothing, so never rely on it for private details.
Opens Unscramble Words 4U, our free word-puzzle site, in a new tab. Free, with no sign-up.
Base64 only packages data; it does not lock it. Since decoding takes seconds, it should never be trusted with passwords or personal information.