StreamWriter and UTF-8 Byte Order Marks

c# file-encodings
Kevin picture Kevin · Mar 10, 2011 · Viewed 64.8k times · Source

I'm having an issue with StreamWriter and Byte Order Marks. The documentation seems to state that the Encoding.UTF8 encoding has byte order marks enabled but when files are being written some have the marks while other don't.

I'm creating the stream writer in the following way:

this.Writer = new StreamWriter(this.Stream, System.Text.Encoding.UTF8);

Any ideas on what could be happening would be appreciated.

Answer

HelloSam picture HelloSam · Jul 25, 2012

As someone pointed that out already, calling without the encoding argument does the trick. However, if you want to be explicit, try this:

using (var sw = new StreamWriter(this.Stream, new UTF8Encoding(false)))

To disable BOM, the key is to construct with a new UTF8Encoding(false), instead of just Encoding.UTF8Encoding. This is the same as calling StreamWriter without the encoding argument, internally it's just doing the same thing.

To enable BOM, use new UTF8Encoding(true) instead.

Update: Since Windows 10 v1903, when saving as UTF-8 in notepad.exe, BOM byte is now an opt-in feature instead.

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