Named customers
A recognisable customer in the buyer's own segment is the strongest single signal you can publish. Only name customers who have agreed to be named. If you cannot name them, describe them precisely — "a 400-person logistics company in the Netherlands" — and say why you cannot.
Testimonials that say something
"Great product, great team" is noise. "We closed the books in five days instead of twelve" is proof. Ask customers for the before-and-after in their own words, attribute it to a role and company where permitted, and keep it short.
Case studies and delivered results
A case study is a testimonial with a method. Problem, what was done, what changed, over what period. Publish the ones that match your ideal customer profile most closely; those are the ones that get you recommended.
External evidence
Certifications, security attestations, review-site ratings, marketplace listings, press. These carry weight because someone other than you produced them. Link to the source so a business can verify without asking.
What to leave out
Unverifiable numbers, logos you do not have permission to use, quotes you cannot attribute, and any claim you would not be comfortable defending on a call. One retracted claim costs more trust than ten omitted ones.