What's the best practice for limiting text length in a field?

Question

I have a field on a form that I want to limit to 55 characters due to some constraints with an integration platform we use. I've searched both Google and UX.SE and haven't found any good resources discussing the best way to handle this situation, and it seems like every site I've visited does it a little differently.

I'm going back and forth on what the behavior should be for the user entering the text, should I:

• Truncate/chop off the text at the end, but don't alert the user,
• Not truncate/chop off the excess text, but alert the user to correct the value,
• Or some combination of the above or other alternative?

Edit: Looks like this has also been discussed here

Answer 1

Twitter FTW

I've always thought Twitter has the best solution to this. It allows you to hammer out whatever you like, then edit it down to something that fits. It's extremely clear to the user.

Answer 2

Don't let user type anything longer than 55 characters, and give feedback on how much characters are left when each character entered .

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Edit:

Of course a tooltip informing that user reached the limit would be a nice to have.