When a formula fails in a canvas app, say a connector call that finds nothing, Power Apps shows a red error banner and the control shows nothing. IfError catches the error and gives you a value to use instead, so the app carries on calmly. Here's how it works, with a real error from the Office 365 Users connector.

Len returns how many characters a piece of text has, spaces included. It's the tool for checking a maximum length before you save something, showing "123 of 4,000 characters", and finding spaces you can't see. One formula, one number.

Text typed by people often has spaces you can't see: one at the end of a job title, two between words. They look harmless, but "Sales Engineer " isn't equal to "Sales Engineer", so lookups quietly fail. Power Fx has two functions to clean them up, Trim and TrimEnds, and they don't do quite the same thing.

To show a manager their team, you need the people who report to them. The Office 365 Users connector's Get direct reports (V2), Office365Users.DirectReportsV2(), returns them from Microsoft 365. It has one quirk that trips everyone up: the people are inside a .value table. Here's how to call it, shape the list, and turn it into a simple "is this person a manager?" check.

Approval apps need to know who someone reports to. The Office 365 Users connector's Get manager (V2), Office365Users.ManagerV2() in Power Apps, returns a person's manager straight from Microsoft 365. The catch: for anyone without a manager, it returns an error rather than a blank. Here's how to call it and how to handle that case.

User() gives you a name and an email, but not a job title, department or first name. For those, the Office 365 Users connector has Get my profile (V2), called Office365Users.MyProfileV2() in Power Apps. Here's how to call it, how to ask for only the fields you need, and where to keep the result.

User() tells a canvas app who's using it: their full name, email address, Microsoft Entra object ID and photo. It needs no connector and no setup, which makes it the quickest way to greet someone or fill in "requested by". Here's what each part returns, as seen in Studio, and what User() can't tell you.

A responsive canvas app should work on a phone as well as on a laptop, but you don't need a phone to check. Power Apps Studio can show your app at common phone and tablet sizes, and the canvas itself can switch between four widths while you edit. Testing at a small size early catches layout problems that a wide monitor hides.

While you build, you'll want to use the app the way its users will: select buttons, read the screens, and watch formulas work. Preview runs the app right inside Power Apps Studio, with your real data, without publishing or saving anything. Here's how to open it, close it, and test single controls without it.

Every control in a canvas app has a Visible property. Set it to a formula that's true or false, and the control appears or disappears as the formula changes. It's how you show a My team button only to managers, or a message only when something is missing.