Most “deep” apps require some amount of navigation, moving the user deeper into child views and then back out to the parent view. That navigational backtracking is typically done with a “Back” button, positioned in the top-left corner, and denoted by a pointed left side. You’ve all seen it:

The title of the entire bar is the title of this view; the Back button shows the previous, parent view’s title. Here, then, is a piece of advice for app designers: The Back button should never show the text “Back”. 

This is a widespread issue, present in many extremely popular apps.

This is redundant and it provides no context. Note that Apple never does this, not in any app. Instead, they provide either the full title of the previous view, or an abbreviated/truncated version of it.

Consider the iOS Calendar app:

Apple put three legible, helpful data points into one button. This is the standard to aspire to.

If the previous view is “yours”, as in, titled and populated by you, the developer, you should always have at least a short name for it. (A related point: if you find yourself titling that view Home or Main or Start, you should rethink the app’s navigation completely.) If the view contains user-generated or otherwise unpredictable data, you should specify a reasonable maximum length for the user-generated label, truncating when necessary. As for localization, you’ve presumably already localized that previous view’s title, right?

There’s one more case where even abbreviating or truncating won’t do: a view with an unpredictable, but predictably long title. Apple was faced with this in their Music app (ex “iPod” app). Their solution was to provide a nice, big arrow glyph:

This button provides no context, but it doesn’t have to; the context is already displayed in the toolbar, right next to it. The glyph is small, easy to read, and it requires no localization. If you’re in a similar situation, use this glyph. But, don’t rush to conclude that this is the situation you’re in. Explore the above options first.

Here, then, are your options for Back-button labeling, from the most desirable to the least desirable:

A Back button labeled “Back” is never a good option.