The API: free and Plus
Every DOI's record is open to everyone, with or without a key. A key gives a program an allowance of its own; Plus adds higher limits and a monthly snapshot of the whole registry.
The metadata is the same at every level — open to read, search, download in bulk and reuse, with no fee and no restriction (the policies, section 2). What the levels differ in is service: how many requests a program may make, and what comes ready-made. The limits below are the ones in force today, read from the registry's own settings; they are set to keep every door answering for everyone and may be changed — this page always shows the current ones.
The levels
| What | Without a key | Free key | Plus key |
|---|---|---|---|
| Every read door: the API, the bulk files, the feeds, the citations, the resolver's data | Yes | Yes | Yes |
| Requests a minute | 300 per internet address | 600 per key | 1,200 per key |
| Requests a day (midnight to midnight, India time) | 10,000 per internet address | 100,000 per key | 1,000,000 per key |
| How it is counted | Under a one-way code made from the address — never the address itself — erased within a day | By the key, whatever address it comes from | By the key, whatever address it comes from |
| Your use, day by day | — | On your console | On your console |
| The monthly snapshot: the whole registry in one file (JSON Lines, gzip) with its SHA-256 and a manifest | — | — | Yes — made by the first run of each month; the newest 3 kept (the newest: 2026-10, 928 records) |
| Price | Free | Free | ₹99,999.00 a year + GST in India · $1,000.00 a year outside India |
The same records as the snapshot are open to everyone in the bulk files and in the nightly escrow set; the snapshot is that whole registry made ready once a month, checksummed, for a service that keeps its own copy. Writing — registering, updating, withdrawing — is never counted here; it needs a registrant's sign-in or the registry key, as before.
Getting a key
- Sign in — or make an account; one account works on every Smart Scholars site.
- Make a free key on My DOIs → API keys: one press. It is shown once — copy it then; only its SHA-256 is kept here.
- Send it in a header:
X-Api-Key: ssr_…orAuthorization: Bearer ssr_…— never in the address. - For Plus, upgrade the key below: paid online, it is on Plus at once.
Using it
curl -H "X-Api-Key: YOUR_KEY" "https://registry.smartscholars.in/api.php?action=search&q=food+printing&per_page=3"
Every counted answer says where you stand: X-Api-Level, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset (seconds). Over a limit: 429 with Retry-After and the reason in words. A browser sent on to a DOI's landing page is never counted. All the headers.
The snapshot, with a Plus key:
curl -H "X-Api-Key: YOUR_PLUS_KEY" -o registry-snapshot.jsonl.gz "https://registry.smartscholars.in/snapshot.php?file=latest"
Plus
₹99,999.00 a year + GST in India · $1,000.00 a year outside India, for one key. Sign in, make a free key, and upgrade it here; paid online, it is on Plus at once.
Service facts
- Uptime, as measured — the share of the site monitor's checks of the registry's address that answered. Last 30 days: 100% of 993 checks answered (the record starts 1 Oct 2026). Last 90 days: 100% of 993 checks answered (the record starts 1 Oct 2026). Every check, day by day, is on the status page.
- Support. Anything about a DOI, a record, a policy or the registry's conduct, written to mou@smartscholars.in, is answered within two working days — the promise the policies in force (section 7) make to everyone, with or without a key.
