Free EDI Validator: Validate X12 & EDIFACT Files Online

Paste or upload an EDI file. Pick a version and a transaction type. Get a list of exactly what’s wrong, with the offending segments highlighted in-line. No account creation, no payments, no sales call.

The 4 PM problem

Every EDI integrator knows this moment. A trading partner emails: “Your 850 was rejected.” Attached is a 997 with an AK5 of R and a code you have to look up. Or worse, no acknowledgement at all, just an email or a phone call saying the order never landed.

So you open the file. Six hundred segments of asterisks and tildes. Somewhere in there is a date in the wrong format, a qualifier that isn’t in the code list for that version, or a segment sitting one loop away from where the spec says it belongs.

The usual options are all bad:

• Eyeball it. Fine for a 4-segment file, hopeless for a real one.
• Push it through your integration engine again. Slow feedback loop, and the engine often only tells you that it failed, not where.
• Ask the partner. Now you’re waiting a day per iteration.
• Sign up for a trial of something. Fifteen minutes of forms before you can validate a single file.

The EDI Validator in EDI Generator lets you validate EDI files online, free, and exists to collapse that loop to about ten seconds.

What it actually is

It’s a free X12 validator and EDIFACT validator - a publicly available utility with no login that lets you validate EDI files online against the base standard specifications.

Try it: https://console.edigenerator.com/edi-validator

You give it four configurations (three for EDIFACT):

How to validate an EDI file online for free

Then you paste the EDI into the editor (or hit the upload button and pick a file off disk) and click Validate EDI.

Three layers of checking, in order

The interesting part is that this isn’t one pass. Validation runs as a fail-fast pipeline, and understanding the layers tells you a lot about how to read the output.

Layer 1: The envelope

Before anything else, the interchange envelope is parsed and reconciled: ISA/IEA and GS/GE for X12, UNB/UNZ and UNG/UNE for EDIFACT. This layer catches the structural failures that make the rest of the file meaningless:

• Payload not EDI X12. No start ISA segment or payload too small
• ISA/IEA count error or mismatch
• Invalid number of functional groups
• Zero transaction sets found

It also cross-checks your dropdown selections against the file, which catches a surprisingly common class of bug: validating against the wrong spec and then chasing phantom errors.

• Specified version: 4010 does not match the interchange control version from the EDI (Expected: 00401, found: 00501)

And for X12, the separators you configured are reconciled against the ones actually resolved from the ISA segment. If you told it * but the file uses |, you’re told so directly instead of getting a wall of nonsense parse errors.

If the envelope fails, processing stops there. There’s no point validating transactions inside an interchange that isn’t well-formed.

Layer 2: Structure against the spec

Once the envelope is clean, every transaction in the interchange is walked against the base specification for your chosen version and transaction type.

This is the layer that answers “is this segment allowed to be here, and is anything missing?”:

• Expected mandatory segment BEG. But found segment: “REF*IA*VENDOR-ACCT-123”. [Segment #2]
• Superfluous segment found: “ZZ*INTERNAL*1”. [Segment #24]
• Superfluous segment found: “REF*DP*0038461”. Too many REF segments? [Segment #12]

Notice what the first one really tells you. It isn’t just “BEG is missing”. It’s “I expected BEG at this point and found your REF instead.” That distinction is the whole game when a file is subtly out of order, because the actual defect is usually a segment in the wrong place rather than one that’s absent.

It understands loops, repeat counts, and max-use, so it catches the errors a naive line-by-line checker misses entirely: a required segment omitted, an N1 loop repeated more times than the spec allows, a segment that’s valid in the file but sitting in the wrong loop, a segment repeated past its permitted maximum.

Each transaction in the interchange is validated and reported independently, keyed by its control number (ST02 / UNH01). A 10-transaction interchange where only the third one is broken tells you exactly that.

Layer 3: Elements, codes, and syntax rules

The deepest layer inspects the data inside each segment against the element dictionary:

• Data types: AN alphanumeric, DT dates, TM times, N/R numerics, ID code lists
• Min/max lengths per element
• Code list membership: is 0999 actually a valid Date/Time Qualifier in this version?
• Composite occurrence limits
• Conditional requirements: elements that become mandatory based on the value of another element
• X12 syntax rules: paired (P), required (R), exclusion (E), conditional (C), and list-conditional (L) relationships between elements in a segment

The messages name the segment, the element description, and the element’s dictionary code:

• Segment “DTM” element “Date/Time Qualifier” (i.e. 374): Invalid ID value (i.e. Not allowed): 0999. [Segment #12]
• Segment “REF” element “Reference Identification” (i.e. 127): Is longer than the maximum allowed length: 30. [Segment #7]
• At least one of elements DTM02 (Date), DTM03 (Time) must be present; Syntax rule “R0203” for segment occurring at /N1/[0]/DTM. [Segment #15]

That last category, syntax rules, is the one people most often skip when they hand-roll a validator, and it’s a frequent source of partner rejections.

The results, where you can actually use them

Two things happen when validation completes.

On the right, a results panel breaks down into the envelope plus one card per transaction. Clean ones collapse to a green Valid badge. Broken ones show an error count and expand into the full list.

In the editor, every error is mapped back to its source line. The segment number in [Segment #12] is resolved relative to that transaction’s ST/UNH line, so the offending segments get a red line decoration, a glyph in the margin, and a hover tooltip carrying the message. You’re reading errors on the data, not in a list you have to cross-reference by hand.

A worked example: validating an EDI 850 file

Here’s a small 4010 850 with a deliberate mistake:

ISA*00*          *00*          *ZZ*BUYERCO        *00*VENDORCO       *260825*1156*U*00401*000000001*0*P*>~
GS*PO*BUYERCO*VENDORCO*20260825*1156*1*X*004010~
ST*850*0001~
BEG*00*NE*PO-2026-082501**20260825~
REF*IA*VENDOR-ACCT-123~
PER*BD*JANE DOE*TE*8005550199~
FOB*CC~
DTM*0999*20260905~
N1*ST*BUYER WAREHOUSE #4*92*004~
N3*123 LOGISTICS WAY~
N4*DALLAS*TX*75201~
N1*VN*VENDOR SUPPLIES INC*91*V-98765~
PO1*001*100*EA*12.50*PE*CB*ITEM-SKU-101*VN*VEND-SKU-A~
PID*F****WIDGET MODEL A - RED~
PO1*002*50*EA*25.00*PE*CB*ITEM-SKU-102*VN*VEND-SKU-B~
PID*F****WIDGET MODEL B - BLUE~
CTT*2*150~
AMT*TT*2500.00~
SE*17*0001~
GE*1*1~
IEA*1*000000001~

Select X12 / 4010 / 850, separators * and ~, and validate. You get back:

• Envelope: Valid. ISA/IEA and GS/GE reconcile, ISA12 is 00401 and GS08 starts with 004010, matching the selected version.
• Transaction 0001: errors. The invalid DTM01 qualifier 0999 is flagged, and the DTM line is highlighted in red in the editor.

Now change the version dropdown to 5010 without touching the file. Layer 1 stops you immediately with a version mismatch, rather than letting you burn ten minutes chasing errors that were never real.

EDIFACT Validator Support: First-Class, Not a Bolt-On

EDIFACT support isn’t a bolt-on. Switch the toggle and the entire form re-defaults to D00A, ORDERS, while the version and message-type lists swap to the UN/EDIFACT directories.

The nicest touch: separators are detected from the file as you type. If your payload opens with a UNA service string advice, the element and segment separators are read straight out of it and applied to the editor’s tokenizer live. Paste an EDIFACT file that uses non-standard delimiters and it just works, with no configuration. If the UNA segment is missing, the validator falls back to the standard EDIFACT separators.

Envelope validation follows the EDIFACT model properly, including UNG/UNE group reconciliation and cross-checking the group’s message type and version against what you selected.

What it deliberately doesn’t do

This validator checks your file against the base standard. It does not know that your specific partner requires REF*DP on every line item, needs a 10-digit purchase order number, or rejects anything without a TD5. Those are partner-specific implementation guidelines, and they’re where most real-world rejections come from. A file can be perfectly valid X12 and still be rejected by a partner whose guideline is stricter.

So use the free validator for what it’s outstanding at:

• Confirming a file is structurally sound before you send it
• Diagnosing a rejection when you suspect the file, not the guideline
• Checking a partner’s inbound file when you think they’re the ones out of spec
• Learning the standard: build a file segment by segment and watch the errors disappear
• Sanity-checking generated output while you’re building a mapping

When you need the next layer

Partner-specific validation, saved documents, an EDI-to-JSON model, generation from templates, acknowledgement handling, and connectivity to your trading partners are what EDI Generator does as a product. The free validator is the same engine with the partner layer switched off.

If the free tool keeps telling you your files are valid and your partner keeps rejecting them, that gap is exactly the problem the EDI Generator product solves.

Explore EDI Generator

Frequently Asked Questions

What is an EDI validator?

An EDI validator checks an X12 or EDIFACT interchange against the structural and syntax rules defined by the standard — envelope segments, mandatory and optional segments, loop and repeat limits, element data types, and code lists — and reports exactly which parts of the file don’t conform.

Is there a free tool to validate X12 EDI files?

Yes. The EDI Validator in EDI Generator validates X12 interchanges across 25 versions (3030–7040) and 326 transaction sets, at no cost and without creating an account.

Can I validate EDIFACT files online for free?

Yes. The same tool supports 58 EDIFACT releases (D95A–D24A) and 196 message types, including automatic separator detection straight from the file’s UNA segment.

Does this validator check partner-specific EDI requirements?

No — it validates against the base standard only. Partner-specific implementation guidelines (for example, requiring REF*DP on every line item) are checked by the partner-specific validation layer in the full EDI Generator product, not the free validator.

Do I need to create an account to use the EDI validator?

No. It’s accessible with no login, no payment, and no sales call.