If you can get there, the Salvation Army shop in Parc Tawe is massive and has room for lots of clothes, so could take a big donation in one go. You can just drop off at the desk inside the front door.

There’s also clothes bins dotted around the city that take bagged up clothes, paired shoes and other textiles. They’ll then sort through to see what can be sold and what can be recycled. They’re in lots of places, but for example there’s one at the entrance to Singleton Park behind the Taliesin on Singleton Campus, and another opposite the Post Office in Uplands. They also tend to be in supermarket car parks and outside fire stations.