QSFP vs QSFP28 vs QSFP-DD vs OSFP: Which Form Factor Fits Your Port?
Form factor decides whether a module fits your switch cage. How QSFP+, QSFP28, QSFP56, QSFP-DD and OSFP differ in lanes, speed and optics — and where each one belongs.
Quick answer:QSFP+, QSFP28 and QSFP56 use the same QSFP family footprint at 40G, 100G and 200G. QSFP-DD adds a second row of contacts for 400G, while OSFP uses a different outline for 400G and 800G. Choose by your switch's port type, not by the module alone.
How the form factors differ
All QSFP-family modules use four electrical lanes; QSFP-DD adds a second row of contacts for eight lanes, and OSFP uses its own outline and connector layout. Lane count and lane speed together set the maximum rate: 4×10G for QSFP+, 4×25G for QSFP28, 4×50G for QSFP56, 8×50G for QSFP-DD 400G and 8×100G for 800G OSFP.
Form factors at a glance
The table maps each form factor to its rate, lane layout and the optics we stock. Product pages carry the exact reach and interface for each SKU.
| Form factor | Typical rate | Lanes | Optics in our catalog |
|---|---|---|---|
| QSFP+ | 40G | 4 × 10G | 40GBASE-SR4 / ESR4 / IR4 / LR4 / ER4 |
| QSFP28 | 100G | 4 × 25G | 100GBASE-SR4 / LR1 / ER4 / ZR4 |
| QSFP56 | 200G | 4 × 50G | 200GBASE-SR4 / DR4 / FR4 / LR4 |
| QSFP-DD | 400G | 8 × 50G (DR4 uses 4 × 100G) | 400GBASE-SR8 / DR4 / FR4 / LR4 |
| OSFP | 800G | 8 × 100G | 800GBASE-SR8 |
Mixing form factors in one switch
The cage decides compatibility. QSFP+ and QSFP28 share the QSFP footprint, but the port must support the module's speed. QSFP-DD cages are built to accept QSFP-family modules on many platforms, while OSFP has a different outline and is not interchangeable with QSFP-DD. Confirm the switch model and port type before ordering.
400G: QSFP-DD or OSFP?
Both form factors carry 400G, but they are not interchangeable — the switch port sets the choice. In our catalog, 400G is supplied as QSFP-DD (SR8, DR4, FR4, LR4) and 800G as OSFP (SR8, eight 100G lanes). Check the port label and the vendor's optic guide, then confirm coding with us.
Browse the high-speed families
Every family is coded for your switch model before shipping. Share the port type, link distance and switch software version for a confirmed part number.