Open AI File

Information, tips and instructions

AI File Format

AI is a file extension used by Adobe Illustrator application to store its documents. Adobe Illustrator is a software which was first released by Adobe in 1982 and is already 37 years old. During this period of time and multiple version releases (for software 37 years is very long) AI format experienced several changes.

Current Adobe Illustrator AI file format is essentially an EPS file format conforming to Adobe Systems' Document Structuring Conventions with additional Adobe Illustrator specific features added with every new version. Additional features include operators which reference Adobe Illustrator specific procsets (procedure sets). These procsets could include Adobe Illustrator specific brushes, styles, textures, etc. These operators are not fully documented and interpreting them in third party software could be problematic. Also, these operators are typically not supported during import from AI file to other applications.

Prior to Adobe Illustrator version 8 AI file format was based on restricted syntax conforming to Document Structuring Conventions. This restricted syntax language was called PGF.

For compatibility with third party applications both EPS and PGF versions of AI files could include full PDF version of graphics stored inside the file if “Save with PDF Compatibility” option is enabled. This way any application which supports PDF files is able to open AI file.

Adobe Illustrator AI documents could be in revisable or final form. Revisable document format contains information necessary to edit the document but not needed for printing. Final form documents contain only information necessary for printing and certain editing features may not function properly.

Most recent file format specification is not available for AI file thus it is impossible for third party vendors to read AI files. AI file format specification is available for download here. It includes format for the following Adobe Illustrator versions:

  • Adobe Illustrator 1.0/1.1
  • Adobe Illustrator 88
  • Adobe Illustrator 3.0/3.2
  • Adobe Illustrator 4.0
  • Adobe Illustrator 5.0/5.5
  • Adobe Illustrator 5.x, Japanese Edition
  • Adobe Illustrator 6.0
  • Adobe Illustrator 7.0
  • Adobe Illustrator EPS (Encapsulated PostScript)