It's a fair question to ask of any tool in this category, since "offline" gets used loosely enough in software marketing that it's worth checking what a vendor actually means by it before relying on the claim mid-project.
refern states this directly on its own site: core library, canvas, search, viewing and study workflows work without an internet connection, and the library stays on your device rather than a server. No account is required to use the app at all — their own words are "you do not need an app account."
What still touches the network
refern publishes a short, specific list of what it does use the internet for: initial licence activation, update and trial-time checks, optional downloads for its on-device tagging components, feedback, and saving media from the web. Everything on that list is either a one-time or occasional event, not something the app depends on while you're actually searching or arranging a board.
Worth reading that list against your own workflow rather than taking the one-word "yes" at face value — a licence check on activation is nothing to plan around, but an optional download for on-device tagging components is the kind of line worth noticing if you were counting on a fully airgapped setup from the first launch.
~/Pictures/Reference- Client boards
- Location scouts
- coii-thumbnailswritten by Coii Ref
- coii-proxieswritten by Coii Ref
- coii.dbwritten by Coii Ref
Where this matters in a real workflow
The practical upshot: a studio day with no wifi, a flight, or a server refern's company eventually stops running doesn't take your library with it. Your boards and files stay in normal folders on disk, and refern says explicitly that files and data remain accessible even after a trial expires — you keep the folder, whatever the app does next.
That's a genuinely local-first design, and it's one of the few claims in this category worth taking at the vendor's word because it's checkable: the same local-first standard, and what it actually guarantees, is worth reading in full before assuming every "works offline" claim in this space means the same thing.
Why "offline" means different things across this category
Not every tool that survives a dropped connection was built that way from the start. Some apps cache recent data so a lost connection is tolerable for a session, then need to reconnect to sync changes, check a licence, or reach features that live on a server. refern's description reads differently — the library is the disk copy, full stop, and the network list is short enough to publish in one sentence rather than described as "most things work offline" with no specifics. That distinction is worth checking for any tool in this category, not assuming from a marketing line that says "offline mode" without saying what still needs a connection.
Where it's a close call, not a coin flip
refern and Coii Ref land on the same side of this question, which is not the whole comparison — refern is the more capable app on most other axes, including an on-device tagger and search-by-meaning that Coii Ref doesn't have. The full comparison covers where each one actually wins, and what people move to when refern isn't the fit covers the rest of the field if offline was the deciding question.