Best Synthetic Insulated Jackets of 2025

For those who generate a lot of heat while exercising or consistently deal with jackets growing swampy from the inside out, the Arc’teryx Proton Hoody is worth considering. This jacket is purpose-built for active use in cold weather, pairing a breathable shell fabric with an above-average dose of 80-gram Coreloft Compact insulation (60g in the hood). This combination makes it both warm and versatile enough for dynamic winter use: Our tester wore it while hiking Denali trails in the shoulder season, climbing in New York’s Shawangunks, and commuting through wind chill in New York City. He noted that the jacket provided warmth while hiking in near-freezing temperatures with light layers underneath, but started to feel undertooled when standing around in the wind. Given the jacket’s air-permeable shell, wind and water resistance are notably compromised.

In terms of comfort, the Proton was an instant favorite. The Fortius Air shell is soft and supple with a surprising amount of stretch, offering better freedom of movement than most synthetic jackets. This jacket truly offers a sweatshirt-like vibe, and its quiet fabrics and refined construction also make it feel more premium and approachable than jackets with shiny, techy shells. The build quality is what you’d expect from Arc’teryx: clean seams, rugged fabrics, and refined touches throughout (unfortunately, the pocket zippers do tend to snag).

There are a few downsides to the Proton’s unique design. The soft face fabric will collect wear faster than a more durable, shiny alternative—ours has started to pill under the armpits, and we’re glad we opted for a black model, as the fabric appears capable of absorbing stains. It’s also not great in wet weather, although after a surprise downpour in Anchorage, our tester stayed surprisingly warm even once the outer fabric soaked through—and the jacket dried quickly once the sun returned. The most recent version also runs particularly large, which you’ll want to keep in mind if you’re on the fence between sizes or are looking to layer underneath or over the jacket. And for backcountry use, the Proton compresses down into its hood to about the size of a small loaf of bread, which is bulkier than many ultralight synthetic puffies. Still, the Proton is a bomber choice for anyone tackling cold-weather missions who needs warmth that breathes and a jacket that won’t fall apart at the crag. For more, read our review of the Arc'teryx Proton Hoody.