What Is an EDI File? A Complete Beginner's Guide
If you've ever received a file with an unfamiliar extension like .edi or .x12 from a business partner, and opening it in a normal text editor produced an unreadable wall of text, you've encountered EDI. This guide explains exactly what that is, why it looks the way it does, and how to actually read one.
EDI, Defined
EDI stands for Electronic Data Interchange — the computer-to-computer exchange of business documents in a standard electronic format between trading partners, replacing paper documents like purchase orders, invoices, and shipping notices. Rather than a human filling out a PDF or paper form, EDI lets one company's software generate a structured file that another company's software can read and process automatically, with no manual data entry on either side.
EDI has existed since the 1960s and 1970s, predating the modern internet and XML/JSON-based APIs by decades. Despite its age, it remains the dominant method for high-volume B2B transactions in retail, healthcare, logistics, manufacturing, and finance — largely because it works, it's extremely reliable at scale, and switching an entire industry's infrastructure to something newer is enormously expensive. Large retailers, hospitals, and freight carriers still process millions of EDI transactions every day.
Why Does an EDI File Look Unreadable?
EDI files are plain text, but they're formatted for machines, not humans. Instead of line breaks and labeled fields, an EDI file packs its data into a single continuous stream, using special characters to separate one piece of information from the next. A single line might look like:
CLM*CLAIM0001*250.00***11:B:1*Y*A*Y*Y~
To a human, that's meaningless. To a computer that knows the underlying standard, it's a fully structured record: "This is a Claim Information segment (CLM), the claim ID is CLAIM0001, the total charge is $250.00, the place of service code is 11, the claim frequency is B (adjustment), and so on." The asterisks (*) separate individual data elements, and the tilde (~) marks the end of the segment. A proper EDI viewer reads these delimiters and labels each piece, turning that line into a readable table row.
The Two Major EDI Standards
There isn't one single "EDI format" — there are several competing standards, and which one you encounter depends heavily on your industry and geography.
- ANSI X12 — developed and maintained by the Accredited Standards Committee X12 in the United States. Dominant in North American healthcare, retail, and logistics. Files typically begin with an
ISAsegment. - UN/EDIFACT — the United Nations' international standard, more common in Europe, Asia, and global shipping/logistics. Files typically begin with a
UNAorUNBsegment.
Both standards organize documents around the same basic idea — an envelope (identifying sender, receiver, and delimiters) wrapping one or more transaction sets/messages, each built from a sequence of labeled segments. For a deeper side-by-side comparison, see X12 vs EDIFACT: Formats, Delimiters and Use Cases.
Common EDI Document Types You'll Encounter
Each EDI standard defines dozens of specific document types (called "transaction sets" in X12, "messages" in EDIFACT) for different business purposes. Some of the most common:
- X12 850 / EDIFACT ORDERS — Purchase Order
- X12 810 / EDIFACT INVOIC — Invoice
- X12 856 / EDIFACT DESADV — Advance Ship Notice
- X12 837 — Healthcare Claim
- X12 835 — Healthcare Claim Payment / Remittance Advice
- X12 834 — Benefit Enrollment and Maintenance
How to Actually Read an EDI File
You have three realistic options: use dedicated EDI translator software (built for ongoing automated trading-partner integrations, usually overkill for a one-off read), manually reformat the file in a text editor (tedious and error-prone), or use a free browser-based viewer that auto-detects the standard and delimiters and labels every segment for you. See How to Open an EDI File for a full walkthrough of all three, or jump straight to the X12 EDI Viewer / EDIFACT Viewer to try one immediately.
Try It Yourself
Drop any X12 or EDIFACT file into the free converter and see every segment labeled instantly, with export to CSV, Excel, or JSON. Nothing is uploaded — parsing happens entirely in your browser.
Open the Free EDI ConverterFrequently Asked Questions
Is EDI the same as an API?
No. EDI predates modern web APIs and uses its own file-based standards (X12, EDIFACT) rather than JSON/REST. Many companies now build APIs on top of EDI translation to modernize integrations, but the underlying documents exchanged with most large trading partners are still EDI.
What file extensions do EDI files use?
Commonly .edi, .x12, .edifact, .dat, or even a generic .txt — the extension doesn't reliably indicate the standard; the content's own header does.
Do I need special software to read an EDI file?
You need something that understands the delimiter-based structure. A free browser-based viewer works for occasional reading; ongoing automated processing typically uses dedicated EDI translation software.