- Dungeons and Dragons 5e SDR -- http://dnd.wizards.com/articles/features/systems-reference-document-srd
- Pathfinder SRD -- http://www.d20pfsrd.com/
- DnD 3.5 -- http://www.d20srd.org/index.htm
- 13th Age SRD -- http://www.13thagesrd.com/
- The Archmage Engine -- http://site.pelgranepress.com/index.php/the-archmage-engine-13th-age-srd/
- D20 Modern SRD -- http://www.d20modernpf.com/
- Microlite20 -- https://microlite20.org/
- D20 Advanced -- https://d20advanced.fandom.com/wiki/D20_Advanced_Wiki
- Low Fantasy -- https://lowfantasygaming.com/freepdf/
- Mutants and Masterminds -- http://www.d20herosrd.com/
- Swords & Wizardry -- http://www.swordsnwizardry.com/ (Lite) https://www.drivethrurpg.com/product_info.php?products_id=219477&
- D20 SRD -- http://www.d20swsrd.com/
- OSRIC Pocket SRD -- https://www.drivethrurpg.com/product/111392/OSRIC-Pocket-SRD-PDF
- Open Adventure -- http://geekguild.com/openadventure/
- SE:20 Core Rules SRD -- https://www.drivethrurpg.com/product/309470/SE20-Core-Rules-SRD
- Open Legend SRD -- https://openlegendrpg.com/ and https://github.com/openlegend/core-rules
- Anime d20 — System Reference Document v1.0 -- http://www.opengamingfoundation.org/animesrd/Ability_Scores.htm
- The Arcanum 30th Anniversary Edition SRD -- http://zila-games.com/arcanum/
- BRP SRD -- https://www.drivethrurpg.com/product/307977/BRP-SRD--Editable
- BRP/UGE w/ORC License -- https://www.drivethrurpg.com/product/431991/Basic-Roleplaying-Universal-Game-Engine
- RuneQuest SRD -- http://b5quest.pbworks.com/f/MRQ-SRD.pdf
- QuestWorlds SRD -- https://www.chaosium.com/questworlds-system-reference-document/
- RetroQuest II SRD -- https://viletraveller.files.wordpress.com/2012/01/d100ii_srd_1_3.doc
- RPG-Rules SRD -- https://github.com/coprolit/rpg-rules
- Open Quest SRD -- https://openquestrpg.com/
- Extract of Mongoose Legend SRD -- https://github.com/jeremy-edward-bauerle/LegendSRD
- Renaissance - D100 black powder SRD -- https://www.drivethrurpg.com/product/97426/Renaissance--D100-black-powder-SRD
- Lore / Lore 100 SRD -- https://www.drivethrurpg.com/product/299747/Lore---Lore-100-SRDs
- d100 Bare Metal Edition -- https://github.com/PeterRudin-Burgess/Bare-Metal-Edition
- APOCTHULHU SRD -- https://www.drivethrurpg.com/product/338046/APOCTHULHU-System-Reference-Document
- d00 System SRD -- https://web.archive.org/web/20120622021304/http://d00system.com/index.php?title=Main_Page
- OpenD6 SRD -- http://opend6.wikidot.com/ ; http://opend6project.org/
- What’s O.L.D. is N.E.W -- http://www.woinrpg.com/introduction/ ; https://sites.google.com/site/woinrrd/
- D6 Dungeons -- https://sites.google.com/site/d6dungeons/home
- D6 Core -- https://d6core.com/
- WaRP SRD -- https://www.atlas-games.com/otelegacy#warped/
- Six-Sided Fantasy Reference Document -- http://sycarion.com/static/sixsidedf.html
- Year Zero Engine SRD -- http://frank-mitchell.com/rpg/year-zero-engine-ogl/
- Sixtacular System Reference Document (free) -- https://www.drivethrurpg.com/product/233609/Sixtacular-SRD-10
- Traveller SRD -- http://www.travellersrd.com/
- Cepheus Engine System Reference Document -- https://www.drivethrurpg.com/product/186894/Cepheus-Engine-System-Reference-Document
- 2d6 SF SRD -- https://www.drivethrurpg.com/product/128058/Basic-Character-Generation-2d6-SF-SRD
- Blades In The Dark -- https://github.com/amazingrando/blades-in-the-dark-srd-content
- DungeonWorld -- http://www.dungeonworldsrd.com/
- Trophy SRD -- https://trophyrpg.com/system/
- 24XX SRD -- https://www.drivethrurpg.com/product/335307/24XX-SRD
- Fantasy World -- https://sites.google.com/view/fantasyworldrpg/introduction
- Fate Core -- http://fate-srd.com/fate-core/basics
- Fudge SRD -- http://www.sonic.net/~rknop/php/Omar/fudge/FudgeSRD/
- 2d20 SRD -- https://www.drivethrurpg.com/product/403658/2d20-System-Reference-Document
- Action! System OGL Core -- http://www.sycarion.com/rpg-downloads/action-system-files/
- Drama System -- http://site.pelgranepress.com/index.php/dramasystem-srd/
- Gumshoe -- http://site.pelgranepress.com/index.php/the-gumshoe-system-reference-document/
- Diaspora -- http://www.vsca.ca/Diaspora/diaspora-srd.html
- Bulletproof Blues -- http://ogc.rpglibrary.org/index.php?title=Bulletproof_Blues
- Tango RPG System -- https://sites.google.com/site/tangorpgsystem/
- Basic Fantasy Role-Playing Game SRD -- https://www.dustinian.com/_prototypes/bfrpg_srd.html
- Psi-punk SRD -- http://fudgesrd.opengamingnetwork.com/psi-punk/
- After Sundown SRD -- https://github.com/thegamingden/after-sundown
- DicePunk SRD -- https://www.drivethrurpg.com/product/154330/DicePunk-SRD
- The Exodus System -- https://www.drivethrurpg.com/product/244141/The-Exodus-System
- Exodus Sci-Fi -- https://www.drivethrurpg.com/product/248422/Exodus-System-SciFi-SRD
- Cortex Prime SRD -- https://www.cortexrpg.com/compendium/explore-the-rules/
- Opening the Dark SRD -- https://archive.org/details/OpeningTheDarkSRD
- Heroic Tales -- https://heroictalesrpg.com/
- Ironsworn SRD -- https://docs.google.com/document/d/11ypqt6GfLuBhGDJuBGWKlHa-Ru48Tf3G_6zbrYKmXgY
- Wretched & Alone SRD -- https://sealedlibrary.itch.io/wretched-alone-srd
- Black Spear RPG System Resource Document -- https://www.drivethrurpg.com/product/320985/IronSpike--System-Resource-Document-and-Compatibility-License-for-Black-Spear
- Mark of the Odd (MOTO SRD) -- https://drive.google.com/drive/folders/1C3PgdyvIFf0YdDl-cXpsM_Fr_Vivw5Yj
- Lost & Found Solo System SRD -- https://srd.mousehole.press/
- Personae and Shadowlight -- https://craighatler.itch.io/
- YASS — Yet Another Single Sheet SRD -- https://www.drivethrurpg.com/product/446346/YASS-Yet-Another-Single-Sheet-SRD
- PushSRD — https://capacle.itch.io/push
integrate missing ones from https://www.tenkarstavern.com/p/f.html