Avira (Windows, Mac)
With a reputation for consistently solid performance and easy-to-use tools, Avira is a great choice. The most recent antivirus test from AV-Comparatives gave the pro version a 99.9% protection rate, and you can bet the free version packs similar power.
AVG (Windows, Mac)
Another free antivirus app that’s been very popular for a long time, AVG ranks well in both protection (99.6%) and system resource usage. And while they now offer unnecessary things like system cleanup and mobile antivirus, their core product is still one of the best.
Lavasoft Ad-Aware Free (Windows)
Lavasoft’s pro version of Ad-Aware scored a 99.3% protection rate in recent tests, making it a solid contender. And while that version did tend to use more resources than other antivirus options, it’s still a great choice for Windows users. Its focus on anti-adware and anti-spyware features are especially nice.