Versions 1–1.6 (Illustrator 88)
Development of Adobe Illustrator for the Apple Macintosh began in 1985  (shipping in January 1987) as a commercialization of Adobe's in-house font development software and PostScript file format. Adobe Illustrator is the companion product of Adobe Photoshop. Photoshop is primarily geared toward digital photo manipulation and photorealistic styles of computer illustration, while Illustrator provides results in the typesetting and logo graphic areas of design. Early magazine advertisements (featured in graphic design trade magazines such as Communication Arts) referred to the product as "the Adobe Illustrator". Illustrator 88, the product name for version 1.7,  was released in 1988 and introduced many new tools and features.
Early versions of the software did not support working in preview mode and users needed to have two windows open on their desktop in order to have a live preview of their work. One window to show the work in progress, the other window to show a preview of the work in progress.
Although during its first decade Adobe developed Illustrator primarily for Macintosh, it sporadically supported other platforms. In the early 1990s, Adobe released versions of Illustrator for NeXT, Silicon Graphics, and Sun Solaris platforms, but they were discontinued due to poor market acceptance. The first version of Illustrator for Windows, version 2.0, was released in early 1989 and flopped. The next Windows version, version 4.0, was widely criticized as being too similar to Illustrator 1.1 instead of the Macintosh 3.0 version, and certainly not the equal of Windows' most popular illustration package CorelDRAW. (Note that there were no versions 2.0 or 4.0 for the Macintosh—although, the second release for the Mac was titled Illustrator 88—the year of its release. And there was no version 6 for Windows.) Version 4 was, however, the first version of Illustrator to support editing in preview mode, which did not appear in a Macintosh version until 5.0 in 1993. Version 6 was the last truly Macintosh version of Illustrator. The interface changed radically with the following version to make it more Windows-friendly and consistent between the two platforms. The changes remained until CS6 when some small steps were taken to restore the app to a slightly more Mac-like interface.
With the introduction of Illustrator 7 in 1997, Adobe made critical changes in the user interface with regard to path editing (and also to converge on the same user interface as Adobe Photoshop), and many users opted not to upgrade. Illustrator also began to support TrueType, effectively ending the "font wars" between PostScript Type 1 and TrueType. Like Photoshop, Illustrator also began supporting plug-ins, greatly and quickly extending its abilities.
With true user interface parity between Macintosh and Windows versions starting with 7.0, designers could finally standardize on Illustrator. Corel did port CorelDRAW 6.0 to the Macintosh in late 1996, but it was received as too little, too late. Designers tended to prefer Illustrator, Drawcord, or FreeHand, based on which software they learned first. As an example, there are capabilities in FreeHand still not available in Illustrator (higher scaling percentages, advanced find-and-replace feature, selective round-corner editing, export/print selected objects only, etc.).  Famously, Aldus did a comparison matrix between its own FreeHand, Illustrator and Draw, and Draw's one "win" was that it came with three different clip art views of the human pancreas.
Adobe bought Aldus in 1994 for PageMaker.  As part of the transaction, the Federal Trade Commission issued a complaint of Adobe Systems on October 18, 1994, ordering a divestiture of FreeHand to "remedy the lessening of competition resulting from the acquisition"  because of Adobe's Illustrator software. As a result, Macromedia acquired FreeHand in 1995 from its original developer, Altsys, and continued its development through 2004.
The difference in strengths between Photoshop and Illustrator became clear with the rise of the Internet, Illustrator was enhanced to support Web publishing, rasterization previewing, PDF, and SVG (Scalable Vector Graphics.) Adobe was an early developer of SVG for the web and Illustrator exported SVG files via the SVG File Format plugin.  Using the Adobe SVG Viewer (ASV), introduced in 2000, allowed users to view SVG images in most major browsers until it was discontinued in 2009.  Native support for SVG was not complete in all major browsers until Internet Explorer 9 in 2011.
Version 9 included a tracing feature, similar to that within Adobe's discontinued product Streamline.
Illustrator CS was the first version to include 3-dimensional capabilities allowing users to extrude or revolve shapes to create simple 3D objects.
Illustrator CS2 (version 12) was available for both the Mac OS X and Microsoft Windows operating systems. It was the last version for the Mac which did not run natively on Intel processors. Among the new features included in Illustrator CS2 were Live Trace, Live Paint, a control palette and custom workspaces. Live Trace allows for the conversion of bitmap imagery into vector art and improved upon the previous tracing abilities. Live Paint allows users more flexibility in applying color to objects, specifically those that overlap. In the same year as the CS2 release, Adobe Systems announced an agreement to acquire Macromedia in a stock swap valued at about $3.4 billion and it integrated the companies' operations, networks, and customer-care organizations shortly thereafter. Adobe now owned FreeHand along with the entire Macromedia product line and in 2007, Adobe announced that it would discontinue development and updates to the FreeHand program. Instead, Adobe would provide tools and support to ease the transition to Illustrator. 
CS3 included interface updates to the Control Bar, the ability to align individual points, multiple Crop Areas, the Color Guide panel and the Live Color feature among others. CS3 was released March 27, 2007.
CS4 was released in October 2008. It features a variety of improvements to old tools along with the introduction of a few brand new tools acquired from FreeHand. The ability to create multiple artboards is one of CS4’s main additions from FreeHand. The artboards allow you to create multiple versions of a piece of work within a single document. Other tools include the Blob Brush, which allows multiple overlapping vector brush strokes to easily merge or join, and a revamped gradient tool allowing for more in-depth color manipulation as well as transparency in gradients.
CS5 was released in April 2010. Along with a number of enhancements to existing functionality, Illustrator CS5's new features include a Perspective Grid tool taken from FreeHand, a Bristle Brush (for more natural and painterly looking strokes) and a comprehensive update to strokes, referred to by Adobe as "Beautiful Strokes".
Version CS6 was the sixteenth generation of Adobe Illustrator. Adobe added many more features and several bug fixes such as a new user interface, layer panels, RGB codes, and color ramp to increase performance. CS6 was released on April 23, 2012.
Along with Creative Cloud (the result of Adobe's shift on its release strategy), Illustrator CC was released. This version (the 17th) was the first to be only sold in a subscription-based service model, in line with the other software in the formerly called Creative Suite. As part of Creative Cloud, this version brought improvements in that subject such as color, font and program settings syncing, saving documents to the cloud, and integration with Behance (a creative collaborative network), as well as other features such as a new touch-compatible type tool, images in brushes, CSS extraction, and files packaging .
Starting with version 1.0, Adobe chose to license an image of Sandro Botticelli's " The Birth of Venus " from the Bettmann Archive and use the portion containing Venus' face as Illustrator's branding image. John Warnock desired a Renaissance image to evoke his vision of PostScript as a new Renaissance in publishing, and Adobe employee Luanne Seymour Cohen, who was responsible for the early marketing material, found Venus' flowing tresses a perfect vehicle for demonstrating Illustrator's strength in tracing smooth curves over bitmap source images. Over the years the rendition of this image on Illustrator's splash screen and packaging became more stylized to reflect features added in each version.
The image of Venus was replaced (albeit still accessible via easter egg) in Illustrator CS (11.0) and CS2 (12.0) by a stylized flower to conform to the Creative Suite's nature imagery.  In CS3, Adobe changed the suite branding once again, to simple colored blocks with two-letter abbreviations, resembling a periodic table of elements.  Illustrator was represented by the letters Ai in white against an orange background (oranges and yellows were prominent color schemes in Illustrator branding going back as far as version 4.0). The CS4 icon is almost identical, except for a slight alteration to the font and the color which is dark gray. The CS5 icon is also virtually the same, except that this time the logo is like a box, along with all the other CS5 product logos, with the "Ai" bright yellow. CS6 changed it a bit to a brown square with a yellow border and yellow lettering.
Compatibility with Inkscape:  Inkscape's native format is SVG (Scalable Vector Graphics), which is supported by AI, but the two implementations are not 100% compatible. Inkscape also exports to PS, EPS and PDF, formats which Illustrator can recognize.
|Version||Platforms||Release date||Code name||Notable features|
|1.0||Classic Mac OS||January 1987||Picasso|
|1.1||Classic Mac OS||March 19, 1987||Inca|
|88||Classic Mac OS||March 1988|
|3||Classic Mac OS, NeXT, other Unixes||October 1990||Desert Moose|
|5||Classic Mac OS||June 1993||Saturn||Graph creation, layers, live editing in preview mode|
|5.5||Classic Mac OS, Solaris ||June 1994||Janus||Spell checker, find/replace text function|
|6||Classic Mac OS||February 1996||Popeye||Gradients, eye dropper, paint bucket|
|7||Mac/Windows||May 1997||Simba||Tabbed dockable palettes, transform palette, align palette, Photoshop pixel filters, rasterize, punk, bloat, free distort, layout grid, vertical text tool|
|8||Mac/Windows||September 1998||Elvis||Pencil tool, bounding box handles, smart guides, actions palette, bitmap eyedropper, gradient mesh, live brushes, links palette|
|9||Mac/Windows||June 2000||Matisse||Flash & SVG output, pixel preview, release to layers, drop shadows, transparency, feathering, opacity & layer mask, native PDF support|
|10||Mac/Windows||November 2001||Paloma||Live pathfinder shapes, symbols, slicing, css layer support, ODBC data link, variables palette, save for web, live distortion, warping, envelopes (warp/mesh/top object), liquify tools, grid/line/arc/polar grid tools, flare tool, magic wand|
|CS (11)||Mac/Windows||October 2003||Pangaea /Sprinkles||3D effect, OpenType support, character & paragraph styles, template file format, scribble effect, columns & rows, optical kerning, optical margins, every-line composer, custom tab leaders, WYSIWYG font menu, Japanese type support, path type option, save for Microsoft Office|
|CS2 (12, 12.0.1)||Mac/Windows||April 27, 2005||Zodiac||Live trace, live paint, colorized grayscale, Photoshop layer support, expanded stroke options, control palette, Adobe Bridge support, Wacom tablet support, SVG-t export, PDF/X export, released with an official serial number because of the technical glitch on Adobe's CS2 activation servers as of January 2013 (see Creative Suite 1 & 2)|
|CS3 (13)||Mac/Windows||April 2007||Jason||Live color, Flash integration, eraser tool, document profiles, crop area, isolation mode|
|CS4 (14)||Mac/Windows||October 2008||Sonnet||Multiple artboards, transparency in gradients, blob brush, live gradient editing, separations previews, in-palette appearance editing|
|CS5 (15, 15.0.1, 15.0.2)||Mac/Windows||May 2010||Ajanta||Perspective drawing tools, variable-width strokes, control over opacity in points on gradient meshes, shape builder tool (similar to pathfinder tools) and a bristle brush, which enables users to imitate real life brush strokes while maintaining vector format.|
|CS6 (16, 16.0.2)||Mac/Windows||May 2012||Ellora||Adobe Mercury Performance System, 64-bit memory support, new user interface, gradient on a stroke, pattern creator tool, ImageTrace (replaces Live Trace)|
|CC (17)||Mac/Windows||June 17, 2013||Deeper Creative Cloud integration (font, color palette and settings syncing, Behance integration), new typing capabilities, multiple file place, images in brushes, CSS extraction|
|CC (17.1)||Mac/Windows||January 16, 2014||Live Corners, updated pencil, path reshaping, Typekit integration, custom tool panels|
|CC 2014 (18.0)||Mac/Windows||June 18, 2014||Live Rectangles, pen rubberband, bezier handles no longer grid-snap, Windows GPU performance|
|CC 2014 (18.1)||Mac/Windows||October 6, 2014||CC Libraries, Touch Workspace, Curvature tool, Join tool, auto type area resizing|
|CC 2015 (19.0.0)||Mac/Windows||June 16, 2015||Linked assets in Libraries, Adobe Stock integration, Faster [zoom/pan/scroll], Safe mode, file data recovery, GPU performance, tool and workspace enhancements, Charts preview|
|CC 2015 (19.1.0)||Mac/Windows||July 25, 2015||Stability fixes, Charts update|
|CC 2015.2 (19.2.0)||Mac/Windows||November 30, 2015||Enhanced Creative Cloud Libraries, Shaper tool, new Live Shapes, Dynamic Symbols, enhanced Smart Guides, new SVG Export options, Touch Workspace enhancements, Charts removed|
|CC 2015.3 (20.0)||Mac/Windows||June 20, 2016||Updated and better collaboration with libraries, Work more efficiently with Adobe Stock, Live shapes and transform panel updates, Adobe Experience Design CC (Preview) integration, fast export of assets and Artboards|
|CC 2015.3.1 (20.1)||Mac/Windows||August 10, 2016||New search for Adobe Stock assets|
|CC 2017 (21.0.0)||Mac/Windows||November 2, 2016||Improved alignment tools, find fonts faster, work easier with glyphs, easy access to templates including free Adobe Stock templates, archive and restore all your assets stored in Creative Cloud, introducing Typekit Marketplace, see a live preview by hovering over the font list with selected text, zoom to selection, flat UI and new icons|
|CC 2017.0.1 (21.0.1)||Mac/Windows||January 9, 2017||Stability fixes|
|CC 2017.0.2||Mac/Windows||January 15, 2017||Stability fixes|
|CC 2017.1 (21.1.0)||Mac/Windows||April 5, 2017||Bitmap cropping added; start screen loads faster; color theme panel redesigned; stability enhancements|
|CC "October 2017 release" (22.0.0)||Mac/Windows||October 18, 2017||Properties panel; Puppet Warp; 1000 artboards; Variable and SVG color font support; MacBook touchbar support|