X12 EDI Viewer — Read Any ANSI X12 File Online

How This Viewer Reads an X12 File

Every valid X12 file begins with an ISA segment — the interchange control header. Its exact character positions define the three delimiters the rest of the file uses: the element separator (commonly *), the segment terminator (commonly ~), and sometimes a component/sub-element separator (commonly :). This tool reads the ISA segment first, extracts those exact characters — rather than assuming a fixed set of symbols — and only then splits the rest of the file. That matters because different trading partners configure different delimiter characters, and a viewer that hardcodes "split on ~" will silently produce garbage on a file that uses a different terminator.

Once split, each segment is matched against a segment dictionary (ISA, GS, ST, BHT, CLM, N1, PO1, HL, and dozens more) to attach a plain-English label. Segments the dictionary doesn't recognize are still shown, labeled "Unrecognized / Custom Segment," rather than being dropped — so you always see 100% of the file's content, never a partial view.

The X12 Envelope Structure, Explained

• ISA / IEA — the interchange envelope. One ISA/IEA pair wraps the entire file and identifies the sender, receiver, and delimiters.
• GS / GE — the functional group envelope. Groups one or more transaction sets of the same type (e.g. all the 837 claims in this file).
• ST / SE — the transaction set envelope. Each ST/SE pair is one logical document — one claim, one purchase order, one invoice.
• Data segments — everything between ST and SE: the actual business content (BHT, NM1, CLM, N1, PO1, etc.), specific to the transaction set type identified by the ST segment's first element (e.g. "837", "850", "810").

Which X12 Transaction Sets Can You View?

This viewer is not limited to a single transaction set — it works on any valid X12 file because it parses structurally (by delimiter and envelope position) rather than hardcoding logic for one document type. Commonly viewed transaction sets include:

• 837 — Healthcare Claim
• 835 — Healthcare Claim Payment / Remittance Advice
• 850 — Purchase Order
• 810 — Invoice
• 856 — Advance Ship Notice (ASN)
• 834 — Benefit Enrollment and Maintenance

Viewer vs. Converter: What's the Difference?

This page and the CSV/Excel/JSON conversion pages use the exact same underlying parsing engine — "viewing" and "converting" are really just two views of the same parsed result. If your goal is to read and understand a file, stay here. If your goal is to get the data into a spreadsheet or script, jump to EDI to CSV, EDI to Excel, or EDI to JSON — every export button on this page produces the same output those pages describe.

Also Known As

People also search for this as an "X-12 EDI viewer," "edi viewer convertor," or land here after typing "x12 file won't open" — all describe the same task this tool handles.

Related Guides

New to X12? Start with What Is an EDI File? and X12 vs EDIFACT, then EDI Delimiters Explained for a deeper look at the ISA header mechanics described above.