IF YOU WANT A SPECIFIC VERSION MADE FEEL FREE TO COMMENT!!! 1.3.1 is out! New optional hunger drain tunables, and fixed a stray HUD config file that was generating on dedicated servers.

Passive Health Regen

Out-of-combat healing for players. Stay out of a fight long enough with enough food and you heal up on your own. No potion needed. Made mostly because eating just to top off HP every 30 seconds gets old fast, especially in packs with bigger health pools.

Features

passive out-of-combat healing with configurable delay, hunger gate, and heal rate
optional ramp-up so healing starts slow and builds over time
max health scaling for packs with larger HP pools
saturation bonus with hysteresis, per-HP cost, and flat heal bonus
optional hunger drain (1.3.1+) if you want eating to actually matter
hunger bonus with optional full-hunger tier, and hunger penalty mode
poison and wither healing gates
regen on kill with optional combo stacking
campfire proximity bonuses (1.20.1+)
freezing penalty in powder snow (1.18.2+)
crouch, light level, day/night, and difficulty modifiers
large damage cooldown penalty
reconnect cooldown persistence
custom heart HUD on every version
fancy HUD pass on 1.20.1+ with under-glows, particles, and state priority chain

Defaults

Out of the box:

heal after 5 seconds without taking damage
needs 50% hunger
0.5 HP per heal, every 5 seconds
saturation bonus on
campfire bonuses on (where supported)
freezing penalty on (where supported)
poison and wither gates on Light and steady, not aggressive. All knobs are in the config file.

Versions

Every version has full gameplay and the HUD. 1.20.1+ get the fancy HUD.

1.12.2 Forge
1.16.5 Fabric / Forge
1.18.2 Fabric / Forge
1.20.1 Fabric / Forge / NeoForge
1.20.4 NeoForge
1.21.1 Fabric / Forge / NeoForge Freezing is 1.18.2+ only since vanilla freeze damage didn't exist before 1.17.

Addon

Passive Regen Bandages adds craftable bandages that clear your cooldown and boost healing.

Passive Health Regen [1.21.1]