Split API
Break document bundles into typed sub-documents
Boundary detection finds where each document starts and ends in a compound file, labels it with your types, and returns each one as a standalone file.
What it does
Typed page ranges
Each split returns its type, start and end page, and a file ID you can pass straight to Extract or Classify.
Identifiers per document
An identifier key pulls a value such as an invoice number from each split; strict mode merges adjacent splits that share it.
Performance or Light
Choose the engine per splitter to trade accuracy against cost on long packets.
Under the hood
Segment multi-document files into individual subdocuments.
Large document splitting
High-precision splitting that maintains accuracy on 2,000+ page files.
Instance detection
Detect unique identifiers to separate multiple instances of the same document type, like splitting 50 invoices by invoice number.
Intelligent boundary handling
Smart overlap handles mid-page boundaries while keeping context intact.
Cost-optimized splitting
Toggle cost-optimized splitting for bulk jobs, or high precision for tough files.
Benchmarks
PoliTax Split
72.48%Best boundary-detection F1 with Extend's harness
The 30 largest compound tax filings in the public PoliTax corpus.
PoliTax Split
+8.3 to +28.4F1 points over direct use of the same model
The harness catches about two thirds or more of boundaries for every underlying model.
How to get started
Create an account
Sign up at dashboard.extend.ai. New accounts get 10,000 free credits.
Copy an API key from the Developers page and export it as EXTEND_API_KEY.
Choose how to call Split
Studio: try Split in the browser with no code.
MCP: connect Claude, Cursor, or any MCP client to https://mcp.extend.ai/mcp.
CLI: install with curl -fsSL https://extend.ai/install.sh | sh, then run extend setup.
SDKs: pip install extend-ai or npm install extend-ai; Java and Go SDKs are also available.
Process your first document
Define the document types to look for. At least one type must be other.
curl -X POST https://api.extend.ai/split \ -H "Authorization: Bearer $EXTEND_API_KEY" \ -H "x-extend-api-version: 2026-02-09" \ -H "Content-Type: application/json" \ -d '{ "file": { "url": "https://extend-public-files.s3.us-east-2.amazonaws.com/loan_application.pdf" }, "config": { "splitClassifications": [ { "id": "invoice", "type": "invoice", "description": "An invoice or bill for goods or services." }, { "id": "other", "type": "other", "description": "Any other document type." } ] } }'Move to production
Send production traffic to POST /split_runs; the synchronous POST /split times out after 5 minutes.
Documentation
Use cases
- Flatiron Health case study
Lab & genomic reports
Find the sections of 50-page reports that hold the fields you need before extracting.
- Real estate
Loan & mortgage packets
Separate statements, pay stubs, and disclosures in one closing packet.
- Healthcare
Claims bundles
Break insurance, legal, and healthcare claim packets into typed documents.
- PoliTax Split benchmark
Compound tax filings
Find form boundaries across hundreds of pages of schedules and supplements.
- Splitter product spotlight
Batch scans
Turn one scanned stack into a file per document, ready to route.
- Logistics
Freight paperwork
Separate bills of lading, invoices, and customs forms sent as one PDF.
