1. Leadsie
What it does: Sends a secure link to clients so they can grant access to their Facebook, Instagram, Google Ads, TikTok, etc., in just a few clicks — no manual ID sharing or walkthroughs needed.
2. Flow Agency Tools
Similar to Leadsie, with additional white-label options and onboarding workflows for agencies.
Great if you manage multiple platforms
Allows document collection, client onboarding forms, etc.
3. Manual via Meta Business Manager
If you prefer not to use a tool:
Ask the client to go to Business Settings > Partners
Have them input your Business Manager ID and assign the ad account, page, pixel, etc.
This works, but can be confusing for first-timers, so tools like Leadsie really shine in comparison.
Best Overall:
Leadsie is the most straightforward and widely recommended tool among media buyers and agencies — highly recommended if you want to streamline access without endless back-and-forth emails.