It helps you practice some stuff you already know, but isn't going to help you get better by itself.
Does Blitz Chess Improve your game?
Slow games help a player develop his/her thinking process. Fast games don't really help much in this respect, as the emphasis is on rushing and using thinking shortcuts.

I basically have done nothing but play blitz for about a year and my regular game improved quite a bit over that time. The only problem is I have a really short attention span and only use 10 minutes on a 30 minute clock.

I basically have done nothing but play blitz for about a year and my regular game improved quite a bit over that time. The only problem is I have a really short attention span and only use 10 minutes on a 30 minute clock.
The first 3 years after I became interested in chess all I did was play 3/0 games online. The next 2 years after that I played 5/0 at a club once a week, and continued 3/0 online games. I played at least an hour of blitz about 340 days out of the year. Outside of that I'd look up an opening that gave me trouble and memorize some moves. I might mess with my chessmaster 8000 for an hour once a week or once a month. Sure I improved, I improved each year, but just recently (about a year ago) I started to actually study, and I realize I could have improved a whole lot more if I hadn't been playing blitz at all :)
And when my long game improved, my blitz improved a lot too. When I was playing a lot of blitz, my blitz improved slowly, and my long game improved very slowly.

GM Anish Giri, 15 year old winner of Corus B said that he has reached his level mainly by playing 3 min blitz on ICC (!).
I think one of the main advantages with blitz is you get to see a lot more games per hour. Slow time control and untimed games are vital for improvement too however.
This is misleading to post. First of all, Giri became a GM at 14. You don't become a GM at 14 by merit of anything you did (even if you did study very hard) mostly it's because you were born gifted at chess. One of those who "will become a GM sooner or later."
Secondly, he had chess trainers from a very young age. Having a tremendous amount of talent and a strong study program he had great fundamentals and study habits long before going onto ICC. I might try to guess that playing blitz helped him sort out the tons of information floating around in his young head, but guessing is worthless.
Just because he's a GM doesn't mean the kid understands anything other than chess, he's just a kid, and you can't take what he says about how to improve in chess as if he's an experienced coach. Especially from a GM whose personal experience of improvement has been exceptionally outside of the ordinary. He'd be crazy not to have a warped view of what helps improvement in the average person and what doesn't.
This is why this bit of info is misleading.

Oh, well you're better informed than me. I was just quoting what he said during an interview at Corus.
I think Carlsen has a similar quote about blitz, and how it helped him. And we all know Naka is fond of blitz too. But then there's the 100,000 daily blitz junkies who will never make it to 1600 much less 2600 :) that's how I see it.

I agree with FirebrandX, and I think too much blitz may even be to the detriment of one's game, instilling bad habits for longer games.

Not sure because I play 3|0 all the time. For longer time controls I like to play against bots that are 200-300 rating points higher than me instead of another player online so that I can take my time and explore new ideas, without it effecting my rating (plus bots make their moves instantly). I would recommend trying to beat higher levels on the PlayMagnus app, as I find he plays more human-like than most other bots. 1 year ago I would still lose half the time to Magnus age 8, now I can beat him up to 9 years and 6 months (on a good day). If you can beat Magnus at age 10 at least half of the time then you definitely have the talent to become a chess expert.

I think blitz can actually improve your game but you have to approach it that right way. You have to analyze every game and figure out how you could have played better similar to what you would do after playing a slow game. Many blitz players dont do this though...a more typical blitz player simply plays game after game making the same mistakes over and over again. Personally I dont play much blitz because I know I have a hard time maintaining the discipline of playing it the right way.

It depends. If you are a very fast learner and have a photographic memory, blitz chess will be perfect to help you learn.
I feel that even something like bullet, contrary to what people say about it being a waste of time, can improve depending on how someone learns. Less time means that more games can be played, and helping someone recognize those positions, so it can be good practice.
Speed chess does improve game play, but you must know how to use it to your advantage. In general, the longer the duration, the more likely improvements can be derived.
Just realised this post is at least 10 years old...

Blitz chess will certainly improve your game better than playing no chess at all.
But the absolute best way to improve your game is to study ... and to use your playing time (at whatever timer) to practice what you've learned.

our friend @flatseven seems to stuck in 900s hundred range in blitz even though our friend has played over 4 thousand of games in blitz. You need to be transformed by THE POWER OF THE BIRD, play f4 the bird's eye opening; Leningrad style and the dutch defense (f5 to e4 or the kingside pawns) as black. I got over 250+ ratings in rapid from 1027 to 1300+ in a week, and my blitz rating is at 1200+. I am pushing into the 1400 range rapid, but have stopped blitz for the moment but I will return. With no study and no membership, even though our victim here has diamond membership I have been touched by the appendages of the f pawn. You need to play bird's eye ASAP. FEAR THE BIRD

@optimissed, see what ding liren have to say about online chess
How do you feel about online chess? More and more top players are competing in events like Chess.com’s Speed Chess Championship and Titled Tuesday. Are you a fan?
Not so much. Sometimes before rapid and blitz tournaments, I will maybe play some blitz. But in general I am not going to play too many online games. I think it will sometimes affect your chess ability, because when you play without thinking, it affects your ability to evaluate which move is better in a classical game. If you have played so many moves without too much thinking, you will find it difficult to work out which one is better over the board.
https://www.google.com/amp/s/www.chess.com/amp/article/ding-liren-interview
I have been playing a lot of 5 minute games lately. Is this going to help me improve my game in the long run, or would I do better to study up?