i2c.net
Reference

i2c connector compatibility pairings

Every combination of the connector standards, pre-answered: direct cable, adapter, or level shifter. Prefer the interactive version? Use the compatibility checker.

Qwiic ↔ STEMMA QT
JST-SH · JST-SH
Qwiic ↔ STEMMA (classic)
JST-SH · JST-PH
Qwiic ↔ Grove
JST-SH · Grove 4-pin
Qwiic ↔ Breakout Garden
JST-SH · 5-pin edge
Qwiic ↔ Gravity
JST-SH · Gravity 4-pin
STEMMA QT ↔ STEMMA (classic)
JST-SH · JST-PH
STEMMA QT ↔ Grove
JST-SH · Grove 4-pin
STEMMA QT ↔ Breakout Garden
JST-SH · 5-pin edge
STEMMA QT ↔ Gravity
JST-SH · Gravity 4-pin
STEMMA (classic) ↔ Grove
JST-PH · Grove 4-pin
STEMMA (classic) ↔ Breakout Garden
JST-PH · 5-pin edge
STEMMA (classic) ↔ Gravity
JST-PH · Gravity 4-pin
Grove ↔ Breakout Garden
Grove 4-pin · 5-pin edge
Grove ↔ Gravity
Grove 4-pin · Gravity 4-pin
Breakout Garden ↔ Gravity
5-pin edge · Gravity 4-pin

How to read these

Three things decide every i2c connector pairing

The connector. Same housing and pitch means a stock cable mates them — that's the easy case, and it's why Qwiic and STEMMA QT are effectively one ecosystem. Different housings mean an adapter is doing real work.

The pin order. The dangerous case isn't "won't fit" — it's a plug that fits while disagreeing about which conductor is SDA. Best case the bus goes silent; worst case power meets a data line. The pinout visualizer shows any two side by side.

The voltage. i2c has no negotiation: whatever the host drives reaches every device on the bus. A 3.3 V-only board on a 5 V host needs a level shifter, and no adapter substitutes for one.

Once bridged it's an ordinary bus again — unique addresses (conflicts have fixes), pull-ups in parallel, and a 400 pF budget across the whole run. Compare the ecosystems themselves in the standards reference, or let which connector? pick one for a new project.