What metadata fields should a production load file include, and what do DAT, OPT, and LFP files do?

When electronically stored information (ESI) is produced in litigation or in response to a discovery request, the documents themselves are usually accompanied by a load file. A load file is a structured text file that tells the receiving party’s review platform how to import the production: where each document begins and ends, which images or text files belong together, and what descriptive information (metadata) applies to each record. Parties typically negotiate the production format and metadata set in advance, often in an ESI protocol.

What DAT, OPT, and LFP files do

These three file types frequently travel together in a production:

• DAT (data/metadata file). A delimited text file, one row per document, carrying the metadata fields and often a path to the extracted text. It is the backbone of the load.
• OPT (image cross-reference). Lists each page image in the production and marks where one document ends and the next begins, so single-page images reassemble into multi-page documents.
• LFP (load file for paper/page-level imaging). An older cross-reference format that also maps images and document boundaries, sometimes including OCR and box/folder coordinates.

OPT and LFP perform similar boundary-and-image roles; which one appears depends on the producing tools and the agreed format.

Metadata fields a load file should include

The exact set is negotiated and varies by case, but commonly requested fields include:

• Bates begin / Bates end and any attachment range (parent-child relationships).
• Custodian or source.
• File name, file extension, file size, and hash value (e.g., MD5/SHA) for authentication and de-duplication.
• Date and time created, modified, sent, and received (with the time zone applied).
• For email: From, To, Cc, Bcc, Subject, and date sent.
• Document type, author, page count, and the path to extracted text or OCR.

Why it matters

Producing reasonably usable, accurate metadata supports authentication, search, and chain of custody, and reflects the cooperation and proportionality principles courts expect. Requirements differ by jurisdiction, so confirm the governing rules and any ESI agreement before producing.