It's easy to regret a username choice on the internet, be it because you created it when you were a child or because you feel like it just doesn't reflect who you are anymore. When it comes to gaming, Microsoft has let you change your Xbox Gamertag for some time now, but Sony hasn't been as open with its online IDs on the PlayStation Network. That's about to change, though.
Sony has announced that starting today (or tomorrow, in Europe), you'll be able to change your online ID on PSN, and the first time you do it will be free of charge. After that, it'll cost you $9.99, similar to the pricing on Xbox. IDs can be changed as many times as you want, and you can always revert to any of your previous IDs - they'll remain reserved for you. Reverting is free of charge and can also be done as many times as necessary.
Sony says all titles published on or after April 1, 2018 have been developed with tools that support the ID change, and so those should support the feature. For titles released before that, the change won't be supported, even if they were re-released at a later date.
You also need to be aware of the risks of changing your ID. Even for games released after the specified date, full support for changing IDs might not be included, and this can result in bugs with varying in degree of severity. You may see your old name displayed in-game, lose your progress, or even lose access to additional content you might have paid for. Sony says the majority of most-played titles on the console don't experience issues, though, and it only expects problems to crop up in smaller games. If you do run into any problems, you can contact support to revert your ID to one that didn't have problems.
The change can be made from your account settings on your PlayStation 4 or through Sony's website on a PC. To learn more about ID changes, be sure to read the full FAQ.