You cannot sit in a chair you buy online, so the specification list matters. This checklist uses the US Occupational Safety and Health Administration's guidance on chairs, credited below, and applies it to a real retailer.
1. Check seat height and depth adjustment
The OSHA computer workstations page on chairs says the seat should be height adjustable, especially when shared, and that the seat pan should be depth adjustable so shorter users can sit fully back against the backrest and taller users get support.
2. Check lumbar support
OSHA says the backrest should conform to the natural curvature of the spine and provide adequate lumbar support, ideally height adjustable so it fits the lower back.
3. Check recline
The same page recommends a backrest that can recline at least 15 degrees and lock or be tension-adjusted.
4. Check the armrests
OSHA says armrests should support most of the lower arm and be low enough that shoulders stay relaxed, and that using them is optional. Check whether they adjust.
5. Read the weight rating and the return costs
Heavy-duty ratings are the seller's claim unless a test backs them. Check who pays return shipping on a boxed chair, whether used returns are charged and whether an RMA is required. Keep it unassembled until you are sure.
An example: checking a seller against the list
In our COMHOMA review we applied these questions. The store sells big and tall chairs from about $150 with free delivery, but buyers pay return shipping, used returns can be charged 15% and we found no independent test of weight ratings.
A note on the sources
OSHA is the US workplace safety regulator, and its page is general guidance. We wrote this article in our own words. Some links to brands on this site are affiliate links; see our affiliate disclosure.