Arbitration is the final stage of an Upwork fixed-price dispute, in which an independent arbitrator reviews the contract and the evidence and makes a binding decision on the escrowed funds, once both parties have paid a fee set by Upwork.
If mediation ends without agreement, either side can escalate. Upwork's process then requires each party, and Upwork itself, to pay a fixed fee to an external arbitration provider; the amount is stated in the Help Center and may change. A party who does not pay within the time allowed is treated as having withdrawn, and the escrow is released to the other side. If both pay, the arbitrator considers the contract terms, the milestone descriptions, the submitted work and the messages, and rules on how the funds are split. The ruling is final under Upwork's Terms of Service.
The fee is the point. It is set high enough that arbitration over a small milestone costs more than the milestone, so almost every dispute is settled in mediation or abandoned before this stage. For a large contract it is the only route to a binding outcome, and the party with the better-documented case usually prevails, which is why experienced freelancers keep scope, changes and deliveries inside the contract.
Arbitration applies to fixed-price escrow only. Hourly disputes are decided by Upwork against the Work Diary and do not go to an arbitrator. The process also sits apart from the general arbitration clause in Upwork's Terms of Service, which governs disputes between a user and Upwork Inc. rather than between a client and a freelancer.
How Upwork Insights uses it
This term describes Upwork's own rules or product rather than a figure the index measures; the pages that do carry live figures are the stats and rate pages.