The version included in Mac OS X v10.5 added read and write support for Office Open XML and OpenDocument Text.

The version included in Mac OS X v10.6 added automatic spelling correction, support for data detectors, and text transformations.

Formatted text, justification, and even the inclusion of graphics and other multimedia elements are supported by TextEdit, as well as the ability to read and write to different character encodings, including Unicode (UTF-8 and UTF-16).

The high-resolution TextEdit 1.5 icon found in Mac OS X versions starting with 10.5 (Leopard) features an extract from Apple's "Think different" ad campaign.

Apple formerly distributed TextEdit's source code as part of the documentation of its integrated development environment (IDE) Xcode.