The Sidewinder is a rapid-fire micro-missile launcher. It is effective against large targets, but lacks precision due to its large spread. The micro-missiles it fires do not yield a large area effect on detonation, due to their shaped-charge design.
The Sidewinder is an anti-Titan weapon that makes it easy for the Pilots to damage enemy Titans. The micro-missiles do limited damage, but may do critical damage by hitting vulnerable spots. It has a rather high fire rate with a high magazine capacity to boot. It should be advised that it is useless when rodeo attacking a Titan, because the missiles will explode on impact, killing the pilot.
It is mainly effective at close range where it can hit vulnerable spots and deal critical damage. It is less effective at medium range, where it can at least hit an enemy. For long range, other anti-titan weapons are preferable.
The Sidewinder returns in Titanfall 2, though rebranded as the Sidewinder SMR. It has also changed categories; instead of being an Anti-Titan weapon, it is now a Grenadier weapon, and can be equipped as a Pilot primary, alongside AT weapons such as the Archer Heavy Rocket and Mag Launcher. It is competent against both infantry and Titans, being able to kill enemy Pilots in only two shots. It requires lead to keep its projectiles on target, however.
The Sidewinder's magazine size and fire rate have steadily increased over development, from 10 (with what appeared to be a slow fire rate and relatively high accuracy) to 15, to the current 25 (and relative scatterfire), changing it from an odd niche weapon to what is essentially a low accuracy rocket-launching assault rifle.
Though it was classed as an anti-Titan weapon in the original game, it was also effective against pilots and grunts.
In the Titanfall 2 mission Trial By Fire, the Sidewinder appears as part of the default Pilot loadout.