The maximum length for common essay is 650 word. Is it OK if I have 10 words more?
Yes it would be bad. There is a limit for a reason. If it just 10 words extra try to cut down a little and make it more concise.
The common app software wont let you enter over 650 words
Both of the above posters are correct. Mine ended up being coincidentally exactly 650 words. I tried entering another to see what would happen, and the systems prompts you and won’t allow it. @Soccerchic24 is correct. If you can’t say what you want in 650 words, you are doing the thing wrong and it is bad.
You might have a word or two leeway depending on how the app counts your words. There was another thread in which the OP was concerned because the word count in Word (let us assume) was two more than the common app showed. I wouldn’t count on that, however,
It seems that everything counts when you are being evaluated by Admissions. Don’t chance it. Good luck.