The biggest CLIP models we know of are open source.

If a company has a bigger CLIP model they don't have even reported that.

Also OpenAI had already for a moment a proprietary CLIP model that was bigger than any other models available, the CLIP-H used by Dalle 2.

As someone who is out of the loop but could use high quality image embeddings right now, what's the best CLIP model right now?

it really depends on what you're trying to achieve, if you want to build a semantic image search then a small/base model would be fine, I think that bigger models usually leak to much information that makes the embeddings space to difficult to interpreter for simple algorithm like cosine similarity, if you want to condition a generative model then a bigger model should provide more information about the prompt or the image.

SDXL uses OpenCLIP, and then OpenAI CLIP as a backup basically to allow it to spell words properly, but I think you could replace the second one.

Stable Diffusion switched to OpenCLIP for stable diffusion 2. But it looks they went back to clip for the xl version.

People complained about openclip not being as good. Hopefully we can have a better and open clip model eventually.