How can I detect the encoding/codepage of a text file


Question

In our application, we receive text files (.txt, .csv, etc.) from diverse sources. When reading, these files sometimes contain garbage, because the files where created in a different/unknown codepage.

Is there a way to (automatically) detect the codepage of a text file?

The detectEncodingFromByteOrderMarks, on the StreamReader constructor, works for UTF8 and other unicode marked files, but I'm looking for a way to detect code pages, like ibm850, windows1252.


Thanks for your answers, this is what I've done.

The files we receive are from end-users, they do not have a clue about codepages. The receivers are also end-users, by now this is what they know about codepages: Codepages exist, and are annoying.

Solution:

  • Open the received file in Notepad, look at a garbled piece of text. If somebody is called Fran├žois or something, with your human intelligence you can guess this.
  • I've created a small app that the user can use to open the file with, and enter a text that user knows it will appear in the file, when the correct codepage is used.
  • Loop through all codepages, and display the ones that give a solution with the user provided text.
  • If more as one codepage pops up, ask the user to specify more text.
1
288
10/3/2014 12:40:13 PM

Accepted Answer

You can't detect the codepage, you need to be told it. You can analyse the bytes and guess it, but that can give some bizarre (sometimes amusing) results. I can't find it now, but I'm sure Notepad can be tricked into displaying English text in Chinese.

Anyway, this is what you need to read: The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!).

Specifically Joel says:

The Single Most Important Fact About Encodings

If you completely forget everything I just explained, please remember one extremely important fact. It does not make sense to have a string without knowing what encoding it uses. You can no longer stick your head in the sand and pretend that "plain" text is ASCII. There Ain't No Such Thing As Plain Text.

If you have a string, in memory, in a file, or in an email message, you have to know what encoding it is in or you cannot interpret it or display it to users correctly.

257
7/11/2013 8:12:59 AM

If you're looking to detect non-UTF encodings (i.e. no BOM), you're basically down to heuristics and statistical analysis of the text. You might want to take a look at the Mozilla paper on universal charset detection (same link, with better formatting via Wayback Machine).


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