Detect base64 encoding

Question

Does anyone know of a jQuery plugin that can check if text is base64 encoded by chance? I want to be able to decode base64 strings but only if the string is encoded to begin with. I see several scripts out there that can encode and decode but I really one that can check if the string is encoded.

Does such a thing exist?

Related Q: http://stackoverflow.com/questions/3355407/validate-string-is-base64-format-using-regex#3355534 — Incognito, Aug 19 '11 at 20:17
Does this answer your question? [RegEx to parse or validate Base64 data](https://stackoverflow.com/questions/475074/regex-to-parse-or-validate-base64-data) — Wiktor Stribiżew, Jan 11 '22 at 09:51

score 11 · Accepted Answer · edited May 23 '17 at 12:18

11

Must it really be a jQuery plugin? Just use a simple JavaScript regex match:

var base64Matcher = new RegExp("^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})$");

// ...

if (base64Matcher.test(someString)) {
    // It's likely base64 encoded.
} else {
    // It's definitely not base64 encoded.
}

The regex pattern is taken from this question: RegEx to parse or validate Base64 data.

edited May 23 '17 at 12:18

Community

1
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answered Aug 19 '11 at 20:24

BalusC

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Nope.. I can make the extension myself. Thank you. – Nick Aug 23 '11 at 03:13
It fails for some text, e.g. "Grey" is a base64 encoded character which is not. – Ihsahs Sep 26 '14 at 12:23
That's exactly why the answer says "likely" instead of "definitely". – BalusC Sep 26 '14 at 12:40

score 4 · Answer 2 · answered Sep 23 '13 at 19:18

The above answer didn't count for the padding with equals signs (= or ==) at the end of the string for me. I've updated the query and the following works for me.

var base64Matcher = new RegExp("^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})([=]{1,2})?$");

Marylyn Lajato · Answer 3 · 2017-02-26T15:22:57.277

I know this might be late to answer but this is what I came up so far. In this case, I use the {match} in jQuery. This is applicable for images or texts. Hope this helps

var sSampleBase64Text = 'data:text/plain;base64,MSkgTG9naW4gRGV0YWlscwogPj4gdGNfYWRtaW5fYXllZQogPj4gdHdpbmtsZXMyMnRo';
var mCheckMatchResult = sSampleBase64Text.match(/^(?:[data]{4}:(text|image|application)\/[a-z]*)/);

var sAlertMessage = 'Valid base 64 encode string';
if (mCheckMatchResult === null || mCheckMatchResult.length <= 0) {
     sAlertMessage = 'Not a valid base 64 encode string';
} 

$('.result').append('<p>' + sAlertMessage + '</p>');

Try to look this up here: https://jsfiddle.net/lajatomary/a8tugwe3/4/

score 0 · Answer 4 · answered Jul 13 '20 at 20:06

Just encountered this and found a solution that might be helpful:

function safeBase64Encode(testString) {
  try {
    // If it's encoded, it will look the same in atob(btoa()) and btoa(atob())
    let isEncoded = btoa(atob(testString)) == atob(btoa(testString))
    if ( isEncoded ) {
      return testString
      }
  } catch (err) {
    // If we get an error like it's not a valid encoding, you gotta encode it.
    return btoa(testString)
  }
}

Detect base64 encoding

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