Two open tabs can save different versions of one record. Check whether your website detects that conflict. RUN A CONTROLLED TEST Open one record in two tabs in a test environment. Change and save its description in the first. In the second, try saving the older version with another edit. Record what happens to the first change. Do not use real prices or orders for this exercise. CONDITIONAL UPDATES MDN describes If-Match as an ETag matching condition; a mismatch returns 412. This can help prevent lost updates when the API implements the check. Adding a client header alone does not create protection. OFFER A HUMAN NEXT STEP Explain that the record changed and invite the editor to review current data. Do not erase entered text without warning. Decide together whether the workflow needs manual comparison, reopening or a separate confirmation action. Do not blindly retry the save automatically. CHECK EVERY ROUTE Test the ordinary form, bulk editing and integrations where your product has them. Behavior should be consistent. A report needs only a test identifier, action sequence and result without private content. When planning a website for a domain from the catalogue, establish who may edit content simultaneously. Include this scenario in the development brief: it tests preservation of the team's work, not merely the appearance of a success message. Image: a new AI photoillustration for this article; a conceptual scene, not a documentary photograph. Domain catalogue: https://domainevery.com/en/domains Primary sources: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/If-Match https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/ETag
