Automotive Aftermarket Ecommerce One catalog, many storefronts, each one different.

Selling parts online used to mean one website. Today the same part may be listed on a webstore, eBay Motors, Amazon, Walmart Marketplace and Google Shopping at once, and each of them wants the catalog in a different shape. The brands and retailers that grow online are the ones whose catalog data can keep up with all of them.

How big online parts buying has become

Online buying is no longer a side channel for anything. The US Census Bureau reports that ecommerce made up 17.1% of all retail sales in the second quarter of 2026 [1].

The aftermarket is a large and growing pool for that shift. The Auto Care Association forecasts the total US aftermarket at $599.7 billion in 2026, and puts the average age of light vehicles on the road at a record 12.9 years [2]. Auto Care's joint ecommerce research with MEMA Aftermarket Suppliers forecast about $44.6 billion in US online sales of aftermarket parts for 2025 when Amazon, eBay Motors and Walmart are included, and about $23 billion without those marketplaces [3]. The same research finds do-it-yourself buyers more inclined to buy from online-only sources, and projects the whole online channel, marketplaces included, to grow 6.7% a year from 2020 to 2030 [3] [4].

Every channel takes the catalog its own way

The industry has two standards built for exactly this job. The Aftermarket Catalog Exchange Standard (ACES) carries fitment, meaning which vehicles a part fits [5]. The Product Information Exchange Standard (PIES) carries product information such as descriptions, attributes, pricing, packaging and digital assets [6]. Both are published by the Auto Care Association. The catch is that each sales channel accepts them differently, or not at all.

The details matter. eBay states that listings with parts compatibility get a boost in its search results, and its Guaranteed Fit program shows buyers a fit check when their vehicle matches [7] [8]. Amazon's Part Finder relies on ACES data, and Amazon warns that not every seller who asks to send fitment directly will be accepted [9]. Walmart notes that not all PIES data maps into its catalog [10]. None of these rules is hard on its own. Meeting all of them at once, from one catalog, is where most teams struggle.

The identifiers that hold it together

Fitment only helps if the channel can attach it to the right product, and every channel does that with identifiers. A Global Trade Item Number (GTIN), the number behind a UPC barcode, is the GS1 key that identifies a trade item [13]. Google asks for a GTIN where the manufacturer has assigned one, requires a manufacturer part number when there is no GTIN, and requires a brand for new products [12]. Amazon lets sellers without a GTIN apply for an exemption [14].

Brand and part number have to agree everywhere. Amazon matches ACES records to listings on brand name and a normalized part number [9]; Walmart matches mainly on brand and manufacturer part number [10]. A part number typed one way in the fitment file and another way on the listing is a part with no fitment, however good the fitment file is.

When the catalog cannot keep up

The cost of a catalog that cannot feed every channel is mostly invisible. A listing without fitment cannot be checked in Amazon's Part Finder [9], misses eBay's search boost for compatibility [7], and does not appear in Walmart's fitment widget, which shows only listings with fitment on file [11]. The part is for sale; shoppers searching by vehicle simply never see it.

Speed matters too. Amazon says matching new fitment to products can take up to three weeks for new products, and that incorrect fitment comes off only when matching delete records are sent [9]. A catalog that cannot produce deletes leaves old mistakes live.

Then there are returns. The National Retail Federation estimated that 19.3% of online sales would be returned in 2025 [16], and Auto Care credits its data standards with reducing returns [17]. Accurate, complete data on every channel is the part of that number a catalog can control.

• Parts that are listed but invisible to vehicle searches
• Corrections that wait weeks, or never arrive
• The same product described differently on every channel
• Staff re-keying data for each marketplace by hand

What a channel-ready catalog looks like

• One source of truth. Fitment and product data are maintained once, in the industry standards, and every channel is fed from that single catalog.
• Each channel gets its own shape. ACES where it is accepted, a channel's own template where it is not, and clean identifiers for channels such as Google that use no fitment at all.
• Identifiers are consistent. Brand, part number and GTIN match exactly across the fitment file, the product data and every listing.
• Changes flow both ways. New fitment goes out, and removed fitment goes out as deletes where a channel needs them.
• Universal parts stay universal. Fluids, tools and other products with no vehicle fitment are listed as exactly that, not forced into a vehicle list.

What to ask before you expand online

Whether the work is done by software, a service or an in-house team, these questions show how well it will hold up as channels are added:

1. Can one catalog feed every channel in the format that channel accepts, without re-keying data?
2. Does it check that brand, part number and GTIN agree before anything is sent?
3. When fitment is removed, are delete records produced for the channels that need them?
4. Can you see what each channel actually shows after a send, not just what was sent?
5. How quickly does a correction made once reach every channel?
6. If you change providers, does the catalog, with its fitment and product data, stay yours?