For each optional rule, I will list the page number. In some cases, I've noted some things as options even though the books don't explicitly call them out. Race and class availability are prime examples of this.
This list was inspired by +Shawn Sanford.
- Ability scores (13)
- Race selection (17)
- Human traits (31)
- Class selection (45)
- Alignment (122)
- Equipment sizes (144)
- Multiclassing (163)
- Feats (165)
- Skills with different abilities (175)
- Encumbrance (176)
- Initiative (189)
- Playing on a grid (192)
- Renown (22)
- Feywild magic (50)
- Shadowfell despair (52)
- Outer Planes (59-67)
- Loyalty (93)
- Villainous class options (96, 97)
- Buying and selling magic items (135)
- More difficult identification (136)
- Alternatives to Epic Boons (230)
- Automatic success (239)
- Only players award Inspiration (241)
- Miniatures (250)
- Flanking (251)
- Diagonals (252)
- Facing (252)
- Madness (258)
- Milestone XP (261)
- Level advancement without XP (261)
- Proficiency dice (263)
- Ability check proficiency (263)
- Background proficiency (264)
- Personality trait proficiency (264)
- Honor and Sanity (264-266)
- Fear (266)
- Horror (266)
- Healing variants (266, 267)
- Rest variants (267)
- Plot points (269)
- Initiative variants (270, 271)
- Action options (271)
- Hitting cover (272)
- Cleaving (272)
- Injuries (272)
- Massive damage (273)
- Morale (273)
- Spell points (288)