Both ways.
BoardGameGeek, both ways
BoardGameGeek is where the games' facts live, and where plenty of collections already are. GameChest brings yours in by username. It can also send back to BGG which games you own, once owned, have pre-ordered or want to buy, which you're selling or trading, and the editions you picked, always after showing you every change.
Game facts and covers come from BGG, asked for by GameChest's server rather than your browser, and each cover is kept as GameChest's own copy.
Updated
Bring the collection in
Type your BGG username and GameChest reads the collection BGG shows publicly under that name; no password is needed. This is what lands where:
| On BGG | On your shelf |
|---|---|
| Owned | Have |
| Owned and for trade | Have · Selling |
| Pre-ordered | Pre-ordered |
| For trade, not owned | Have · Selling |
| Previously owned | Had (Sold) |
| Wishlist, want to buy, or want in trade | Radar · Want to buy |
| Wishlist priority 5, “Don't buy this” | Left out |
| Only rated or played | Left out |
Had arrives marked Sold; change how it left on the game's page. Expansions are marked as expansions (if BGG doesn't say which they are at the time, a later refresh from BGG does). A game already on your shelf, whatever its answers, is skipped, so bringing the collection in twice adds nothing twice.
Plays come in separately, from Settings → BGG; the answer to What comes in from BGG? has the details.
Changes go back, shown first
A sync checks first and lays out the whole plan, both ways: what would change on BGG and what would change here. Nothing changes on either side until you say so. When the two disagree, the newer change wins, and a tie goes to your shelf. A clash is shown to you, never forced: for instance, a game you marked Want to buy here after BGG had it as owned.
A change you skip is remembered, and that exact change isn't proposed again, unless you choose Forget declines in Settings → BGG.
Games you have as owned (marked for trade if you're selling or trading them), games you Had as previously owned if they're already in your BGG collection, games you want to buy as wishlist, and Pre-ordered games as pre-ordered. Never Pledged games, Radar games you don't want to buy, games with no BGG link, plays, notes, prices or loans.
Do you own it?
What are you doing with it?
On your shelf: Have
A sync tells BGG: owned, and not previously owned or on the wishlist.
A pre-order or for-trade mark on BGG can come off too.
Pre-ordered goes as BGG's pre-ordered flag, which hasn't yet been checked against BGG itself. If BGG doesn't keep it, a later check shows that game still out of step.
What a sync tells BGG for each answer, when the change here is the newer one, worked out by the sync's own code. The game is invented.
Your BGG password
It's used once, to sign in to BGG as you, and is never stored or logged. It's only asked for when something needs changing on BGG.
When BGG changes something
Reading from BGG uses its public API. Sending changes back relies on signing in to BGG as you, which BGG can change at any time, so the sync may stop working now and then.
What if BGG changes something?
The BoardGameGeek page says what GameChest takes from BGG and what it sends back.
Try it on your own shelf
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