Frequently Asked Questions
How do I encode text to Base64 and decode it?
Paste your text (or load a file) and the tool encodes it to Base64 instantly — or, with a Base64 string as input, decodes it back. Use Auto-Detect to guess the direction, or Force Encode / Force Decode to be explicit. Toggle URL-safe mode if the string is for a URL. Then copy or download the result. Everything happens in your browser; nothing is uploaded.
Does this upload my data, and does it work offline?
No upload, and yes it works offline. All encoding and decoding happen in your browser using JavaScript — there's no server receiving your text or files, no logging, and no tracking. That matters because people Base64 tokens, keys, and files. Once the page has loaded it keeps working with no internet connection, which you can confirm in your browser's network tab.
What is Base64 and how does it work?
Base64 represents binary data as text using a 64-character alphabet (A–Z, a–z, 0–9, +, /). It takes your bytes three at a time — 24 bits — and splits them into four 6-bit groups, each mapped to one character, padding the end with = when the input isn't a multiple of three bytes. The result is plain ASCII that can travel safely through text-only channels like email and JSON.
Is Base64 encryption or secure?
No — this is the most common misconception. Base64 is an encoding, not encryption. It doesn't hide, scramble, or protect anything: anyone can decode a Base64 string in one click and read the original data. It exists to move binary safely through text channels, not to keep secrets. If you need to protect data, use real encryption — Base64 offers zero security.
What's the difference between standard and URL-safe Base64?
The alphabet. Standard Base64 uses + and /, which have special meaning in URLs and filenames. URL-safe Base64 (Base64url) swaps those for - and _, and often drops the = padding, so the string is safe to drop into a URL, query parameter, or filename. The catch: decode with the same variant used to encode, or the +/ versus -_ characters won't line up.
Can I encode images and binary files to Base64?
Yes. Load a local file — an image or any binary — and the tool reads it in your browser and encodes it to Base64, without uploading. This is exactly how data URIs work: you can take the result and embed an image directly in HTML or CSS as data:image/png;base64,…. Just remember Base64 adds about 33% to the size, so large files make large strings.
What does Auto-Detect do?
Auto-Detect inspects your input and guesses whether you want to encode or decode, so you don't have to set the mode manually for the common cases. If the input looks like valid Base64, it decodes; otherwise it encodes. When the guess isn't what you want — or your text happens to look like Base64 — switch to Force Encode or Force Decode to make the direction explicit.
Why does Base64 make data bigger?
Because it trades size for text-safety. Every 3 bytes of input become 4 output characters, so the result is roughly 33% larger than the original (before padding). That's the cost of representing arbitrary bytes using only 64 printable characters. Base64 is for safe transport and embedding, not compression — if size matters, compress the data first, then Base64 the compressed bytes.
What is Base64 padding (the = signs)?
Padding fills the output to a multiple of four characters. Base64 works in blocks of three input bytes producing four characters; when the final block has only one or two bytes, one or two = signs are appended to complete the block. So Hi (2 bytes) encodes to SGk= with a single pad. URL-safe Base64 often omits padding, which is why some strings have no = at all.
Can I decode Base64 back to a file or image?
Yes. Paste a Base64 string (or a data URI) and decode it, and the tool reconstructs the original bytes — which you can download as a file. For an encoded image, decoding gives you back the image. This is handy for pulling an asset out of a data URI or checking what an encoded blob actually contains. Use the same variant (standard or URL-safe) it was encoded with.
Can it handle large files?
Usually yes, within your device's limits. Because everything runs locally, the constraint is your browser's memory and CPU rather than a server cap. Small and medium files are instant; very large files produce very large Base64 strings (remember the ~33% growth) and can be slow or memory-heavy. Nothing is uploaded regardless of size — it's purely a matter of local performance.
Is it free, and are there limits?
Yes, completely free — no payment, no signup, no account, and no usage caps or watermarks. Since everything runs in your browser, there's nothing for us to meter; the only practical limit is your device's performance on very large inputs. Use it as much as you like, including offline once the page has loaded.
Still have questions?
If you can't find the answer you're looking for, feel free to contact our support team.