Later this year, the signers of the New York Agreement intend to implement a consensus rule change on bitcoin that will cause a hard fork and chain split. It is very concerning that those signatories include a large number of companies that hold bitcoins on behalf of users.

Included in the list are blockchain.info, coinbase, purse.io, shapeshift.io, xapo and circle.

Even more concerning are some of the online statements made by the individuals who control these companies, such as u/evoorhees, his twitter, indicating ignorance about the difference between soft forks and hard forks and, worse, indicating serious contempt for users who don't toe the line.

But no matter what, if your coins are on one of the above mentioned online wallet providers, or with any of the signatories of the New York Agreement (the full list is here), if and when they abandon the consensus rules that have governed bitcoin since 2009 and begin enforcing an incompatible chain, your coins on the original chain may be forever inaccessible to you.

You have plenty of time right now to download and install a proper wallet. A wide variety is available at https://bitcoin.org/en/choose-your-wallet . When you click on any of the icons on that site you'll see a list of features. Choose a wallet whose first point is "Control Over Your Money". Download and install it. And then SEND ALL YOUR COINS FROM THE ABOVE PROVIDERS TO YOUR WALLET. Fees are lower now than they have been all year. (I sent a transaction yesterday for five cents.) Then, when you've confirmed that you've received your coins make sure to make at least one backup of your wallet somewhere else. (You can also back up your wallet before you've sent coins to it. It is magic internet money after all.)

If you leave your coins on those providers, after the hard fork they may tell you that you don't own coins on the original chain. They may tell you whatever the hell they want to tell you. If you have your coins on your computer or phone, whatever they say matters not a bit. Look at Erik Voorhees own comments on twitter where he states "We will absolutely run Segwit2X" and on reddit and ask yourself, "Do I unequivocally trust that guy with my bitcoins?" If the answer is no, and you have coins on his service, get them off. If he or any of these other companies makes your coins inaccessible to you on the original chain or steals them on that chain, you will have little recourse then and nobody to blame but yourself.

This is, moreover, the way bitcoin was meant to be held – by you and not by an intermediary.

Final note, if there is a chain split on August 1st because this New York Agreement fails to do what it promised, you'll want your coins in your own wallet by then too.

TLDR: Install a wallet on your device and move your coins there now while fees are low and before any hard fork threatens to make it impossible for you to control your coins that are on an online wallet provider.

(Since I know this question will come up, I recommend bitcoin core, bitcoin knots and electrum from personal experience. I'm currently running bitcoin knots).