Open Library Covers

Overview

Use Open Library search results to identify the right book and cover, then build a covers.openlibrary.org image URL. Prefer cover IDs from search results when available because they avoid ISBN mismatch issues across editions.

Official docs:

Covers API: https://openlibrary.org/dev/docs/api/covers
Search API: https://openlibrary.org/dev/docs/api/search

Workflow

Search for the book with enough fields to evaluate identity and cover data.

curl -sG 'https://openlibrary.org/search.json' \
  --data-urlencode 'title=The Power Broker' \
  --data-urlencode 'author=Robert A. Caro' \
  --data-urlencode 'fields=key,title,author_name,first_publish_year,cover_i,isbn,editions,editions.key,editions.title,editions.isbn,editions.cover_i' \
  --data-urlencode 'limit=5'

Choose the result by matching title, author, and edition context. Do not blindly trust an ISBN already in a file; stale or wrong ISBNs can point to unrelated covers.
Prefer identifiers in this order for final cover URLs:

cover_i / editions.cover_i -> https://covers.openlibrary.org/b/id/<cover_id>-M.jpg
exact ISBN for the edition -> https://covers.openlibrary.org/b/isbn/<isbn>-M.jpg
edition OLID from /books/OL...M -> https://covers.openlibrary.org/b/olid/OL...M-M.jpg

Verify the chosen URL exists by appending ?default=false. A 200 means Open Library has an actual cover. A 404 means the normal URL would return a blank placeholder.

curl -I 'https://covers.openlibrary.org/b/id/240727-M.jpg?default=false'

For site pages, use the display-size URL directly in the image source:

<img src="https://covers.openlibrary.org/b/id/240727-M.jpg" alt="Book Title" class="book-cover-small">

Cover URL Reference

Book cover pattern:

https://covers.openlibrary.org/b/<key>/<value>-<size>.jpg

Supported book keys:

id for Open Library internal cover IDs, usually from cover_i
olid for edition IDs like OL7440033M
isbn
oclc
lccn

Sizes:

S small thumbnail
M medium display image
L large image

Use M for reading-list covers unless the local page design requires a different size.

Practical Search Commands

Search by title and author, returning compact rows:

curl -sG 'https://openlibrary.org/search.json' \
  --data-urlencode 'title=Alien Clay' \
  --data-urlencode 'author=Adrian Tchaikovsky' \
  --data-urlencode 'fields=title,author_name,first_publish_year,cover_i,isbn,key' \
  --data-urlencode 'limit=10' \
| jq -r '.docs[] | [.title, (.author_name // [] | join(", ")), .first_publish_year, .cover_i, ((.isbn // [])[0]), .key] | @tsv'

Search all text when title/author fields miss:

curl -sG 'https://openlibrary.org/search.json' \
  --data-urlencode 'q=Alien Clay Adrian Tchaikovsky' \
  --data-urlencode 'fields=title,author_name,first_publish_year,cover_i,isbn,key' \
  --data-urlencode 'limit=10'

Validate several candidate cover URLs:

for url in \
  'https://covers.openlibrary.org/b/id/123-M.jpg?default=false' \
  'https://covers.openlibrary.org/b/isbn/9780000000000-M.jpg?default=false'
do
  printf '%s -> ' "$url"
  curl -s -o /dev/null -w '%{http_code}\n' "$url"
done

Selection Rules

Prefer a cover_i from the matching work or edition when the current ISBN returns the wrong cover.
If search returns multiple plausible works, verify using the Open Library work page (https://openlibrary.org/works/OL...W) or edition page (https://openlibrary.org/books/OL...M) before editing files.
Keep alt text as the local book title, not the Open Library result title, if the local title is intentionally styled or expanded.
Do not crawl or bulk-download covers. The Covers API is rate-limited for non-cover-ID lookups and intended for public page display.
Include a courtesy link to Open Library when adding broader attribution surfaces; for simple existing reading-list image fixes, keep the established site style unless asked to redesign attribution.