The point of this page is to try and help to get my head around when all of the editions of 40k came out. People online (and in real life!) often refer to the glory days of fifth edition, for example, and I have no idea what that means – was it 10 years ago? 20? Well, if you’re like me, you can wonder no longer!
First edition (1987)
The very first edition of Warhammer 40k bore the subtitle of Rogue Trader, and had much more of a RPG feel to things. Throughout this period, the background was being developed, including the Horus Heresy backstory and stuff about the Orks and the Chaos gods.
Second Edition (1993)
Second edition took the lore to a very dark place, really emphasizing the grim dark feel and the hopelessness of the Imperium situation. Special Characters from the setting became a big thing at this time, as well, leading to the popular moniker “Herohammer”.
Third Edition (1998)
The first major rules re-write. While first edition was pretty skirmish-based, things had been moving more towards bigger battles, and third edition introduced many xenos races such as the Necrons and Tau, as well as branching out the codex structure generally, rather than publishing army lists through White Dwarf and other supplements. The biggest thing was how streamlined the game became, with movement standardised and the system becoming based solely on D6.
Fourth Edition (2004)
This edition was backwards-compatible with many of the recently-released codexes. There were some tweaks to line of sight, but on the whole things were kept the same as previously. Two new expansions for the game were produced at this time: Cities of Death, and Apocalypse. Battle for Macragge was the starter set for this edition.
Fifth Edition (2008)
Fifth edition saw the beginning of finecast replacements for metal figures, and while previous editions had sought to streamline the rules, this time around, many rules (and models) were added back in, albeit in a new way. Rules such as Power from Pain (for Dark Eldar) and Imperial Guard Orders were brought back at this time. Also: true line of sight became a thing! Assault on Black Reach was the starter set for this edition.
Sixth Edition (2012)
Psychic Power cards are introduced! Flying vehicles also got a proper subset of rules, and several other aspects were reworked for this edition. Imperial Knights were also introduced as a playable model, and rules for greater interactivity with scenery were also added in. Dark Vengeance was the starter set for this edition.
Seventh Edition (2014)
My edition! The first one I played in, anyway. The actual Psychic Phase was introduced, and Maelstrom of War became a thing. In addition, the Lord of War slot – previously models produced specifically for Apocalypse – became playable in regular 40k.
Eighth Edition (2017)
The most radical redesign since Third Edition, with a complete overhaul of the rules – a slimmed-down version of which was released for free online. The lore was also moved along, with the galaxy torn in half by the cicatrix maledictum. And primaris marines were born! Dark Millennium was the starter set for this edition.
Ninth Edition (2020)
Mainly a tweak from Eighth, with most of the rules backwards-compatible. The Psychic Awakening series that came out at the end of the previous edition made for a much more smooth transition. Indomitus was the starter set for this edition.
spalanz.com 
This is a very helpful resource, thank you for putting it together. My mental map of 40k editions over time is very much tied to what was happening in my “real life” at the time, and as I get older (and the number of editions gets longer!) that gets harder to navigate. I got into the game during 4th edition, although I was aware of it from late 3rd. It wasn’t until 5th that I really got into it in a big way though (just in time to have no disposable income to spend on it – but that was 2008 for all of us wasn’t it!).
I hope you don’t mind me having one tiny “well actually…” moment but Assault on Black Reach was the starter for 5th Edition (Orks vs Space Marines ). I can’t remember the name of the 3rd edition starter but it was Black Templars vs Dark Eldar. Assault on Black Reach was my first starter set, I remember saving up for it carefully and still have all the models (all painted too!) squirreled away somewhere. The Ork half of the box became the seed from which the rest of my Ork army grew.
Argh! Thanks for the clarification! I’m currently reading Helsreach – so I knew 3rd edition was Black Templars, and just assumed they’d be up against Orks, so put Black Reach down there!! I’ve amended my post, thanks very much for that!
I’m a relative newcomer, coming in near the start of 7th edition, so a lot of this is very muddy in my brain when people talk in terms of editions etc. Putting it together has been really interesting though, as you can really see the frequency with which they come out. I also thought it interesting that there have only really been, what, 2 major rules overhauls in the history of the game, otherwise things have just been refined and refined each time.