If you use the Python client, do not base64-encode js_snippet yourself - the client does it, and double-encoding sends garbage the browser cannot run. Pass cookies as Cookie objects rather than a raw string, and remember the client defaults to browser on and datacenter proxies; override proxy_type when you need residential. Need async? Install the async extra or the async methods do not exist.

Context: scrapingant-client-python README: the client base64-encodes js_snippet automatically, takes cookies as Cookie objects with name and value, and defaults proxy_type to datacenter and browser to True. The async variant needs the [async] install extra.