The question of whether to use a comma before too is simultaneously very complex and extremely simple, depending on how you look at it. Too is an adverb that can be used in one of two ways: as an amplifier and to mean also, in addition. The former case is straightforward, so we’ll deal with it first.
Too as an Amplifier
In this case, you use too before an adjective or adverb to denote that there is a more of the given quality of the adjective or adverb it amplifies. No commas are needed here.
They are way too much into linguistics. ✔
They are way, too much into linguistics. ✘
Too as Also, In Addition
This is where things get complicated. Most of us have been taught during schooling that you should always put a comma before too, especially at the end of a sentence. Simple, right?
Well, no. There is no grammatical rule dictating this. Aha, so no comma before too! Therein lies the problem. While no rule dictates it, it has been a writing convention for so long that people may feel it is necessary and correct you if you don’t place a comma before too.
However, the English language is generally trending towards simplicity (as most languages do) and has been for some time. If you’ve ever studied a foreign language, you’ve gotten to know those pesky cases (nominative, genitive, etc.) that give everyone trouble. English had them in the past, too, but became simpler over time.
That is also the general trend when it comes to punctuation, including commas. People prefer to use them less nowadays. You see the conflict now, right – for a long time everyone was taught to use a comma before too, even though no rule dictated it, and nowadays people want fewer commas, including before too, even though no rule dictates it.
So, what should you do? Take your pick, depending on the situation. We’ll explain some common preferences people have to help you make an informed decision.
Comma Before Too at the End of a Sentence
To reiterate, both of these sentences are grammatically correct:
I have no idea when to use a comma, too. ✔
I have no idea when to use a comma too. ✔
If you are writing a school paper or scientific article and the teacher or editor constantly corrects you on the usage of commas before too (in whichever direction), just go with their preference, it will be easier.
In addition, some people prefer to use a comma before too when it refers to the object of the sentence, but not when it refers to the subject. Once again, this is not a grammatical rule, we are simply explaining what you may encounter. So, in that case:
I like the Lord of the Rings and Mean Girls, too.
Oh, you like LOTR and Mean Girls? I like them too.
Comma Before Too in the Middle of a Sentence
This situation is similar to the previous one. There is no rule regulating the use of too in the middle of a sentence, so it is up to you. That being said, commas are useful tools that indicate a pause. If you want your sentence to have a pause, such as if the speaker had an abrupt change of thought and you want to emphasize it, use a comma before and after too.
I too like dancing in the moonlight. ✔
I, too, like dancing in the moonlight. ✔
Both sentences are correct, but the second one indicates that the speaker just realized they have something in common and wanted to emphasize it.
What’s the Bottom Line?
When too is used as an amplifier no commas before or after are needed.
You have far too much time on your hands if your hobby is reading about punctuation. ✔
You have far, too much time on your hands if your hobby is reading about punctuation. ✘
When it is used to mean also, in addition, no grammatical rule dictates whether you should use a comma, so do as you feel most comfortable.
I was quite surprised by his actions too/,too. ✔
Caesar too/,too, was caught off-guard by Brutus. ✔
In case you get corrected on your usage of commas with too, you will know why it happened. Whether you want to contest the corrections or just go with the flow is your choice. As a side note, regardless of how you decide to use a comma with too, use it that way consistently in your writing – that’s always good writing advice.