Written and maintained by CASRAI Editorial Board
Last updated
Who this is for: researchers, librarians and data managers who need to find, download, reuse, cite or mine historical biodiversity literature, and who need to pick the right access route for the job. Facts checked on 2026-11-07 against BHL’s own pages.
What is the Biodiversity Heritage Library?
The Biodiversity Heritage Library is, in its own words, “the world’s largest open access digital library for biodiversity literature and archives.” It is a digital library of scanned books, journals and archival material, not a list of protected places. The similarly worded phrase “biodiversity heritage site” refers to a different idea (designated heritage areas), and BHL does not publish a count of such sites.
Who runs it and what it covers
BHL is an international consortium of natural history, botanical, research and national libraries. It is a global consortium rather than an independent nonprofit: the Council on Library and Information Resources (CLIR) hosts it administratively and acts as fiscal sponsor. In April 2025 BHL announced that the Smithsonian would stop hosting its administrative and technical operations after 1 January 2026.
According to the BHL about page, the collection spans the 15th to the 21st centuries, with hundreds of thousands of volumes and more than 64 million pages. More than 300,000 freely reusable images are on Flickr. Scientific names in the text are indexed using Global Names Architecture tools. BHL also carries an Acknowledgment of Harmful Content, because historical material can contain outdated or harmful content.
How to search and download
- Search. Full-text search covers bibliographic metadata and the OCR text of page images. Short fields such as titles rank higher. Advanced search is at biodiversitylibrary.org/advsearch.
- Search inside a book. In the book viewer, use the Search Inside tab at top right.
- Download a whole book. Choose Download Contents, then Download Book, then PDF. For indexed articles use Download Article.
- Download selected pages. Use Select pages to download, then Review, then Generate My PDF. BHL emails a confirmation number and a link.
- Single page images. A high-resolution JPG is at biodiversitylibrary.org/pageimage/[pageid]; a JP2 option is also offered.
- Plain text. Download Contents, then OCR.
- Citation and metadata files. Download Citation gives BibTeX or RIS; MODS is available from the View Metadata page.
Reusing and citing BHL material
BHL claims no copyright on its files, but the underlying works can have rights. Check the Copyright & Usage section or the Show Info tab for one of three labels.
| Label on the item | What it means for reuse |
|---|---|
| Public domain | Reuse is allowed, including commercial reuse. In the US, works published more than 95 years before the current year are in the public domain. |
| No known copyright restrictions as determined by the scanning institution | Treat with caution; this is the scanning institution’s determination, not a guarantee. |
| In copyright. Digitized with the permission of the rights holder. | Usually licensed CC BY-NC-SA 4.0; check the License Type and Rights Holder fields. For commercial use, contact the rights holder, since BHL does not intermediate. |
Flickr images follow the same rules as the BHL item they come from. BHL’s preferred attribution is: “Image from the Biodiversity Heritage Library. Contributed by [Holding Institution]. | www.biodiversitylibrary.org.” When citing, use stable URLs and DOIs where assigned (see persistent identifier), and the BibTeX or RIS export. For licence terms see Creative Commons.
API and bulk data
Which route to use depends on scale. Details below are from BHL’s developer and data tools page.
| Route | What you get | Notes |
|---|---|---|
| Web viewer | Reading, search, PDF/JPG/OCR/citation downloads | Suited to individual items and pages. |
| API v3 (www.biodiversitylibrary.org/api3) | JSON, XML or SOAP-wrapped XML, including full-text search | API key required (biodiversitylibrary.org/getapikey.aspx). v2 is scheduled for retirement on 31 December 2026; v1 has been removed. |
| Smithsonian Figshare open data collection | Metadata in MODS, BibTeX, RIS, TSV and TXT; full collection or BHL-hosted only | Updated at the beginning of every month. The full OCR text export is 40 GB or more and covers 60+ million pages. |
| AWS Registry of Open Data | Metadata, page images and OCR as individual files | registry.opendata.aws/bhl-open-data; details at github.com/gbhl/bhl-open-data. |
| Internet Archive | Image and OCR downloads | BHL material is hosted there. |
BHL metadata is released under CC0 1.0 and data is provided “as is” under BHL’s Data Disclaimer, without warranty as to accuracy. For general guidance on where such collections sit, see data repository.
Strengths and limits for research use
- Strength: free access to a very large historical corpus, with bulk exports and an API for text mining.
- Limit, OCR quality: OCR was generated by the Internet Archive (Tesseract as of 2020, or ABBYY FineReader). The Show Text tab states whether text is uncorrected, machine-corrected or manually transcribed. Search runs on uncorrected OCR, so it can miss instances.
- Limit, corrections: users cannot correct OCR inside BHL. Crowdsourcing happens through partners such as the Smithsonian Transcription Center, FromThePage and DigiVol.
- Limit, rights: not every item is public domain, so check the label before reuse.
- Limit, content: historical texts may contain outdated or harmful language.
Alternatives
No single platform replaces BHL, because the alternatives below do different jobs. Choose by what you need to retrieve.
| Platform | What it is (per its own site) | When it is an alternative or complement to BHL |
|---|---|---|
| GBIF | An API-accessible service whose documentation lists Species, Occurrence, Occurrence Image, Maps and Literature services. Most use of the GBIF API does not require authentication; a download API handles large requests and search APIs are rate limited. | Use for species and occurrence data rather than scanned books. A complement, not a substitute. |
| Internet Archive | Describes itself as a “Digital Library of Free & Borrowable Texts, Movies, Music & Wayback Machine.” | A general-purpose library. BHL material is also hosted there (see the API and bulk data table), but it has no biodiversity-specific curation. |
| Wikimedia Commons | A volunteer-run repository of public domain and freely licensed educational media; each file’s licence is on its description page. | Useful for reusable images. Check each file’s licence page, and note that BHL’s own images follow the rights label of the BHL item. |
| Flickr Commons | A programme sharing photography archives from cultural institutions; its page lists over 100 members. The page states no single rights statement, so check the individual photo or institution. | BHL also publishes images to Flickr, so the same pictures may appear there with BHL’s rights rules. |
Related resources
BHL holds literature; occurrence records and specimen data live elsewhere. See GBIF, the Darwin Core data standard, and the OBIS ocean biodiversity guide.
FAQ
What is the Biodiversity Heritage Library?
An open-access digital library of biodiversity literature and archives, run by an international consortium of natural history, botanical, research and national libraries, with CLIR as administrative host.
Is the Biodiversity Heritage Library free?
Yes. Reading and downloading are open access, but reuse depends on each item’s rights label.
How many biodiversity heritage sites are there?
BHL is a library, not a register of sites, so it gives no such count. Its own scale is more than 64 million pages.
Does BHL have an API?
Yes. Use API v3 with a free key; v2 retires on 31 December 2026.
Can I use BHL images commercially?
Public domain items can be reused commercially. For items labelled in copyright (usually CC BY-NC-SA 4.0), contact the rights holder.
Sources
- BHL about page (checked 2026-11-07)
- BHL developer and data tools (checked 2026-11-07)
- BHL copyright and reuse (checked 2026-11-07)
- BHL help FAQ (checked 2026-11-07)
- BHL donation FAQ (checked 2026-11-07)
- GBIF API documentation (checked 2026-11-07)
- Internet Archive about page (checked 2026-11-07)
- Wikimedia Commons welcome page (checked 2026-11-07)
- Flickr Commons (checked 2026-11-07)
