Free GMC feed diagnostic

Google Merchant Center Identifier Error Checker

Upload a Google Merchant Center affected-products CSV, a Shopify or WooCommerce product CSV, or paste a feed URL note. The checker groups invalid GTIN, missing MPN + brand, Shopify barcode, duplicate GTIN, and identifier_exists problems into a product-level fix list.

CSV rows disagree?Send a 1-page owner map before bulk identifier edits.

If affected-products rows, Shopify barcodes, feed app mappings, and Merchant Center diagnostics disagree, route the case to the Feed/GMC owner map before changing hundreds of GTIN, MPN, brand, or identifier_exists values.

Send 1-page owner map

Search intent answerUse this checker before editing feed rules or setting identifier_exists=false in bulk.

If Merchant Center says invalid GTIN

Check the source barcode or GTIN shape first: length, check digit, Shopify variant barcode, feed app override, and whether SKU is being reused as a manufacturer identifier.

If it says missing GTIN, MPN, and brand

Compare the affected-products CSV with Shopify or WooCommerce product rows before setting identifier_exists=false or rewriting Merchant Center rules.

If Shopify data and GMC rows disagree

Treat it as a Feed/GMC evidence problem. Use product export, feed mapping, diagnostics screenshots, and public product URLs before bulk edits.

Start with these three inputs

Upload Merchant Center affected-products CSV

Use this for issue title, affected attribute, severity, destination, offer ID, GTIN, MPN, brand, and identifier_exists rows Google already grouped.

Upload Shopify / WooCommerce product CSV

Use this for source catalog evidence: product ID, variant ID, SKU, barcode, vendor or brand, MPN, price, availability, and product URL.

Paste feed URL

Use this when a generated XML, Content API, feed app, or supplemental feed may be transforming correct source fields before Merchant Center receives them.

When to request reviewDo not pay for review when the source owner is obvious. Request it when the CSVs disagree.

Use the free checker

One issue group, source CSV is obvious, and Shopify barcode/vendor/MPN fields match Merchant Center rows.

Copy the action list, fix the product or feed field, and wait for the next Merchant Center fetch.

Request reviewed snapshot

Affected-products CSV, product export, feed app mapping, diagnostics timing, or public product URLs disagree.

Prefill the request with checker counts before bulk edits so the repair owner is decided from evidence.

Escalate to Feed/GMC Fix Pack

Many variants, repeat diagnostics, suspension or Shopping visibility risk, or feed rules can change hundreds of products.

Use the reviewed snapshot as the repair map, then scope implementation only for the confirmed source owner.

Email + store URL are enough to startSend a 1-page identifier owner map before bulk edits.

Private affected-products CSVs can wait for the reply thread. The request carries the current checker counts, issue type, next evidence, and repair-source question into the reviewed snapshot form without asking for every feed file first.

GMC rows0

Product rows4

High-risk groups1

Source ownership matrix

Shopify / WooCommerce product data

Barcode, vendor/brand, MPN, SKU, product status, and channel inclusion are wrong or blank in the catalog export.

Fix the source field before changing Merchant Center rules.

Feed app or Google channel mapping

Catalog rows contain identifiers, but the affected-products CSV receives blanks, transformed values, or SKU-as-MPN output.

Inspect app field mapping, supplemental feeds, and last fetch timing.

Merchant Center feed rule

identifier_exists or identifier fields are overwritten after fetch, especially across many unrelated products.

Review the rule before bulk edits that can suppress valid identifiers.

Public product evidence

The product URL shows a different brand, title, variant fact, or manufacturer claim than the feed row.

Align buyer-visible evidence before requesting a reviewed snapshot.

Sample output preview

What the checker returns before you upload private CSVs.

The output is a source ownership scorecard: every issue group gets a repair owner, the evidence that proves it, and the point where a reviewed snapshot is worth requesting.

Issue groupRepair ownerEvidence that proves itSource ownership scorecard

Invalid GTIN valueShopify product dataVariant barcode is 12345 while Merchant Center flags the GTIN check digit.Review only if a feed app or supplemental feed overwrites the Shopify barcode.

Missing identifiersFeed app mappingShopify export has vendor and MPN, but Merchant Center receives blank brand and MPN.Request reviewed snapshot when ownership is unclear across product export and feed mapping.

identifier_exists mismatchMerchant Center ruleGMC rule sets identifier_exists=false while GTIN or MPN + brand exists in source rows.Review before changing rules that affect many products.

Public evidence conflictPublic product pageFeed claims one brand or identifier while the product URL shows a different buyer-visible fact.Request reviewed snapshot when ownership is unclear between feed data and public proof.

Feed Truth handoff sampleLoad affected-products rows from the Feed/GMC truth workflow.

Use this sample after the Shopify-to-GMC feed truth report points to GTIN, MPN, brand, or identifier_exists repair. It loads matching Merchant Center affected rows and Shopify product rows so the checker can group identifier fixes immediately.

PlatformGoogle Merchant Center affected-products CSVShopify / WooCommerce product CSVFeed URLPaste CSV rows

4 rows checked3 affected rows

Affected-products CSV loaded0

Rows from Merchant Center diagnostics or affected item exports.

Product catalog rows loaded4

Rows from Shopify, WooCommerce, feed app, or pasted product CSV.

Reviewed snapshot trigger1 high-risk group(s)

Add the Merchant Center affected-products CSV or diagnostics screenshot so the checker can match store fields to Google's issue groups.

Next evidence to attach

Attach 3-5 sample product URLs and the matching Shopify export rows before changing GTIN, MPN, brand, or identifier_exists.

Evidence gapAttach the missing source before review.

The checker found affected rows, but review should wait until Merchant Center diagnostics and product catalog evidence can be compared side by side.

High

Invalid GTIN format or check digit

Rows with a non-numeric GTIN, unsupported GTIN length, or failed check digit.

1 row(s). Fix source: Fix the source barcode/GTIN field in Shopify variant barcode, product vendor/brand, the Google & YouTube app, or your feed app mapping.

Medium

SKU may be used as MPN

Rows where MPN equals SKU or looks like an internal store code.

2 row(s). Fix source: Use the manufacturer part number when one exists. Do not automatically map Shopify SKU to MPN.

Reviewed Feed Identifier Truth Snapshot

Use this after the free checker groups the rows. The reviewed snapshot tells you whether the fix should start in Shopify product data, a feed app, Merchant Center rules, or public product evidence.

Reviewed snapshot includes

One-page GTIN, MPN, brand, and identifier_exists repair map.
Affected row grouping by likely source: Shopify product data, feed app, Merchant Center rule, or visible product page.
Priority list for invalid GTIN, missing identifiers, SKU-as-MPN, duplicate barcode, and identifier_exists mismatch.

No listing approval, ranking, policy recovery, or GS1 ownership outcome is guaranteed. The deliverable is a repair map and evidence gap review.

Reserve reviewed snapshot $79

What this can detect

Invalid check digits, missing GTIN, missing MPN + brand, duplicate barcodes, and identifier_exists mismatch.

What this cannot prove

It does not verify GS1 ownership, inspect your Merchant Center account, or guarantee listing approval.

Where to fix

Use the output to decide whether the source is Shopify, WooCommerce, GMC feed rules, or a feed app mapping.

Fix invalid GTIN Missing identifier guide

CSV evidence kit

Prepare the CSV evidence kit before bulk identifier fixes.

Do not edit GTIN, MPN, brand, or identifier_exists rules from one Merchant Center warning alone. Pair the affected-products export with Shopify product rows, diagnostics timing, feed app mapping, and public product evidence so the checker can point to the likely repair source.

Evidence sourceFields to includeWhy it mattersReviewed snapshot trigger

GMC affected-products CSVoffer_id, issue title, attribute name, severity, GTIN, MPN, brand, identifier_existsShows which products Google actually grouped under invalid GTIN, missing identifiers, or identifier_exists warnings.Request review when the same issue appears across many variants or product types.

Shopify product or variant exportvariant SKU, barcode, vendor, product type, handle, title, status, Google channel inclusionShows whether the fix starts in Shopify barcode, vendor/brand, SKU-as-MPN mapping, or channel eligibility.Request review when Shopify has data but Merchant Center receives blank or transformed fields.

GMC diagnostics screenshotdiagnostic date, destination, affected item count, sample products, last fetch or crawl timingSeparates current warnings from stale diagnostics, fetch delays, destination scope, and policy-adjacent evidence.Request review when product counts, diagnostics, and feed fetch timing do not agree.

Feed app or Google & YouTube app mappingGTIN source, MPN source, brand source, identifier_exists rule, supplemental feed or rule overrideShows whether an app, supplemental feed, or Merchant Center rule is overwriting correct Shopify values.Request review before changing rules that affect hundreds of products.

Public product URL evidencevisible brand, product title, variant facts, barcode/GTIN claims, manufacturer identifiers, policy proofKeeps the repair map tied to visible buyer and Google evidence instead of private CSV fields only.Request review when feed identifiers conflict with what shoppers can verify on the product page.

Load evidence into checker Send store URL for Feed/GMC owner map

Identifier decision map

Decide whether GTIN, MPN, brand, or identifier_exists is actually the repair source.

Product identifier warnings look similar in Merchant Center, but the fix can belong to Shopify product data, a feed app mapping, a Merchant Center feed rule, public product evidence, or a broader Google Feed Truth workflow. Use this map before editing hundreds of rows.

Error groupEvidence to inspectLikely repair source

Invalid GTIN valueGTIN length, check digit, Shopify variant barcode, feed app override, and GS1 ownership boundary.Fix the source barcode or GTIN mapping before overriding Merchant Center rules.

Missing identifiersNo usable GTIN and no MPN + brand pair while identifier_exists is true or blank.Add the manufacturer GTIN where it exists, or provide MPN + brand when no GTIN exists.

identifier_exists mismatchidentifier_exists=false with GTIN or MPN + brand present, or true with no usable product identifiers.Set false only when the product truly has no manufacturer-assigned GTIN, MPN, or brand identifier.

Shopify barcode not syncingShopify variant barcode, Google & YouTube app state, feed app field mapping, and last Merchant Center fetch.Choose whether the repair starts in Shopify product data, the feed app, a supplemental feed, or a GMC feed rule.

Check affected CSV rows Load Feed Truth sample

Run the CSV checker

Upload Merchant Center affected-products CSV and Shopify product rows, then group invalid GTIN, missing identifiers, duplicate barcode, and identifier_exists issues.

Start checkerProducts missing in Google?

Send store URL for a Feed/GMC owner map when item counts, diagnostics, fetch timing, feed app ownership, or Google channel state may be the real blocker.

Send store URL for Feed/GMC owner mapFix invalid GTIN rows

Use this when Merchant Center flags invalid GTIN values, bad check digits, SKU misuse, or Shopify barcode source problems.

Open GTIN fixFix missing identifier rows

Use this when Google needs a GTIN, MPN + brand, or a defensible identifier_exists=false decision.

Open missing identifiers fix

Use this before rewriting feed rules.

Product identifier errors often start in the source catalog: Shopify barcode, WooCommerce GTIN fields, brand mapping, or a feed app override. The checker groups the problem before you touch Merchant Center rules.

Keep the boundary clean.

This validates field shape and likely repair source. It does not confirm GS1 ownership, policy compliance, account status, or final Google approval.

FAQ

Questions before uploading product identifier data.

Is this a Google Merchant Center verdict?

No. It is a field-level diagnostic for product identifiers. It does not inspect your Merchant Center account or guarantee approval.

Can this verify whether a GTIN is officially assigned by GS1?

No. The checker validates GTIN length and check digit only. It does not verify official GS1 ownership or brand assignment.

What is the difference between GTIN, UPC, EAN, MPN, SKU, and brand?

GTIN is the global trade item number family, including UPC and EAN. MPN is the manufacturer part number. SKU is usually an internal store code. Brand identifies the maker or brand owner.

Should I set identifier_exists to false?

Only when the product truly has no manufacturer-assigned GTIN, MPN, or brand identifier. Do not use false just to suppress Merchant Center errors.

Why does Shopify barcode not appear as GTIN in Merchant Center?

The issue is usually in variant barcode data, the Google & YouTube app, a feed app mapping, or a Merchant Center feed rule that overrides the source value.

Can I upload Merchant Center affected-products CSV?

Yes. The checker is designed for affected-products CSV exports and product catalog CSVs. The data is processed in the browser.

What Shopify export columns should I compare with GMC identifier errors?

Start with variant SKU, barcode, vendor or brand, product title, handle, product status, Google channel inclusion, and any feed app GTIN, MPN, brand, or identifier_exists mapping fields.

Does this replace my feed app?

No. It helps identify where the field problem likely starts. The actual repair still happens in Shopify, WooCommerce, a feed app, or Merchant Center rules.

Can agencies use this for client stores?

Yes. Agencies can use it as a first-pass triage before producing a client fix list or ordering a deeper feed identifier audit.