Note: I’ll be on a mostly disconnected vacation this week, and while I’m still planning on posting M-F, expect slower than normal responses from me. If you do write a note though I will get back to you.

Unlike most credit card issuers that deal checking accounts and mortgages, American Express’s main business is cards and it shows: They consistently have the highest sign-up bonus offers, weird authorized user offers, $19,000+ cash back offers, and of course coupon book offers galore. Let’s focus on the first of those today, sign-up bonuses.

When you visit American Express’s website to look at card options, they offer different sign-up bonuses based on:

  • Your browser (Chrome, Brave, Safari, Edge)
  • Your operating system (Windows, macOS, Android, Linux, iOS)
  • How you got to the site (direct, google, bing, baidu)
  • Your browser’s cookies (incognito)
  • Where you’re coming from (mobile network, residential, business)
  • Whether you clicked on an ad
  • When you visit
  • Maybe a dice roll?

If you systematically vary each of the above, you’ll almost certainly find a different sign-up offer. In my quick tests, I was able to see sign-up bonus offers for the American Express Business Platinum card of between 110,000 and 150,000 Membership Rewards by switching my browser and visiting incognito through a search engine on a particular week. But then the next week, no matter which option I chose, the minimum offer for the same card was 110,000 and the maximum was 120,000 Membership Rewards.

What’s the takeaway? When it’s time for a new American Express card, make sure you try several different methods to get the best sign-up bonus. This is true of both Membership Rewards earning cards and co-branded cards like Delta, Hilton, and Marriot AmEx cards. And a final note: never assume that a link from an article will be the best offer. Experiment!

Breaking: The American Express algorithm for sign-up bonuses.