If you mean the series 'Goblin Slayer', the straightforward place I check first is Crunchyroll. I’ve watched both the TV season and the movie on there, and Crunchyroll tends to have the subtitled episodes plus, in many regions, the second season and 'Goblin Slayer: Goblin's Crown' as well. Back when I first binged it I grabbed the English dub through a service that used to handle dubs separately, so if you prefer dubs it’s worth checking the app settings or the dubbing catalog; sometimes regional rights mean the dubbed version shows up on a different platform.
Beyond Crunchyroll, region matters a lot. In Southeast Asia the official Muse Communication channels (like Muse Asia on YouTube) have streamed episodes legally, and platforms like Bilibili serve China. Occasionally Hulu or smaller regional streamers pick up rights for their local catalogues. If you can’t find it on a streaming service, digital storefronts (iTunes, Google Play) or the official Blu-ray release are a safe route. I always double-check the series title 'Goblin Slayer' plus my country in a quick web search — that usually points me to the current legal providers.
Also, heads up on content: the show contains some very mature and upsetting scenes, so check age ratings and viewer advisories before you watch. Personally I reread a few manga panels before rewatching the anime — weird comfort, I know — but otherwise Crunchyroll has been my go-to for everything 'Goblin Slayer' related lately.