Mouser and DigiKey are authorized catalogs: they sell what the manufacturers still make and list, with the datasheets, parametric search and documentation to match. LCSC is a China-market catalog — the same idea stocked from Chinese distributors, including domestic brands the Western catalogs do not carry, which is why a board assembled in China usually starts there. All three are the right answer for a part that is in production, and all three will sell you a single piece. None of them is the right answer for a part that has reached end-of-life, is under allocation, or was never listed at all — that stock is in no catalog, because it is not being offered. It is hunted.
Table of Contents (10 points)
What each catalog actually is
DigiKey and Mouser are franchised, authorized distributors: they buy under contract from the manufacturers, and their catalogs are built from manufacturer listings. That is why the documentation is complete, the search is parametric, and the same part number behaves the same way on every visit. DigiKey is the broader catalog and the one most engineers reach for when identifying an unfamiliar part; Mouser runs the same channel and carries lines the other one sometimes does not. For a part in production, both will sell you one piece, so quantity is not the reason to look elsewhere.
LCSC is a China-market catalog. Its stock comes from Chinese distributors and manufacturers, which covers two things the Western catalogs do not: domestic Chinese brands, and the pricing of the Chinese market itself. It is also the sister of JLCPCB, so for a board assembled in Shenzhen it is the default — parts and assembly share one database.
The difference between the three is not service quality. It is what each one is able to show you: stock that flows from a manufacturer listing in one case, and stock that exists in one market in the other.
The four desks side by side
| Dimension | DigiKey | Mouser | LCSC | ICBOMS |
|---|---|---|---|---|
| Channel | Authorized catalog | Authorized catalog | China-market catalog | Independent spot desk |
| Stock source | Manufacturer listings | Manufacturer listings | Chinese distributor stock | Factory allocation & spot lots |
| Strongest at | Breadth, docs, search | Design-in lines | China-assembled BOMs | Delisted and allocated parts |
| Stops at | A discontinued line | A discontinued line | A part not sold in China | Stock that does not exist |
| Mixed BOM | Quoted line by line | Quoted line by line | Quoted line by line | Kitted into one parcel |
| Lot assurance | Franchise chain, docs | Franchise chain, docs | Depends on the seller | Photos of the actual reel |
Where Arrow and Future Electronics fit
Arrow Electronics and Future Electronics sit on the same authorized tier as DigiKey and Mouser, but they sell it at a different scale: negotiated quotes, allocations and supply-chain programs for OEMs and contract manufacturers buying in volume. That is the channel a production program is set up through, and it is not the desk a buyer calls for a repair order or a hundred pieces.
It is, however, a channel this desk buys from. When a line is still active and the customer wants manufacturer traceability, sourcing it through franchise stock and regional agents is the correct route — the big catalogs are a storefront of that tier, not a rival to it. What the tier does not do is carry a line past its end-of-life notice.
The shift to buying direct from China
Search interest in the Chinese catalog distributors has moved past several traditional Western names, which is the clearest public signal that small manufacturers, start-ups and EMS houses have stopped treating China as a last resort and started treating it as a normal source. The reason is not only price: a small buyer can now see Chinese stock, order from it and have the board assembled, without an agent standing in between.
What that shift exposes is the tail of the BOM. A catalog, Chinese or Western, is a list of what somebody is offering today. End-of-life residual, factory overbuy and buffer stock from completed programs are not offers — they are lots sitting somewhere with an owner who has not listed them. That portion of a BOM is answered by a search and a phone call, not by a storefront, and it is the portion this desk is built around.
What we do with the remainder
- End-of-life lines: the exact variant is fixed first — package, temperature grade, revision suffix — then the allocation market is searched across distributor reserves, factory overbuy and bonded buffer stock. What turns up is inspected before it is offered, not after it is paid for.
- Allocation and shortage: the same search run against a deadline. When the original cannot be found, the cross-referenced alternative is quoted with its differences written out, so the decision to substitute stays with the design owner.
- Mixed BOMs: a sheet of forty lines where six are a problem. We quote all forty, flag which six are hard, and consolidate the result into one shipment instead of six parcels from six sellers.
- Packaging: full reels, trays and tubes where they exist; broken down to the quantity the order actually needs where they do not, in a form an SMT feeder can take.
- Verification before payment: macro photos of the actual reel label, date code and pin finish, sent for sign-off while the parts are still on our bench. That is the standard on every order, whether or not the buyer thought to ask for it.
Machine-readable stock: the API side of the same shift
Part of what buyers now mean by buying online is checking stock without opening a browser: a script, an ERP or an assistant querying availability directly. The Western catalogs answer that with their own APIs. This side of the market is exposed the same way — search and part lookup are described at /openapi.json, and an MCP endpoint at /.well-known/mcp.json lets an assistant query live spot stock and cross-references in one call.
What an API cannot do is confirm that the lot in the photograph is what it claims to be. That check stays physical, and it stays on the desk.
How to choose in one pass
- 01 Part is still in production and documentation matters more than price: buy from the authorized catalog. DigiKey for breadth, Mouser when it holds a line the other one does not.
- 02 Board is being assembled in China and the parts are commodity: LCSC, ordered alongside the assembly.
- 03 Part has reached end-of-life, is obsolete, or is under allocation: stop searching catalogs. Send the full part number with its suffix and ask what physically exists.
- 04 A repair order or a mixed BOM: send the whole list to one desk and have the problem lines flagged, rather than finding them one at a time across four storefronts.
Put this to work on your component list
Send the part numbers or the whole BOM sheet. Each line comes back with current spot availability, original manufacturer condition, and verified cross-references — packed and shipped together in one single parcel.
How this guide is written
Written by the ICBOMS sourcing desk in Shenzhen and reviewed against the manufacturer documents and industry standards the guide cites. Statements are limited to what this desk does and how a part is judged — no indicative prices, lead times or stock counts, because those are quoted per line against a live check. Each guide carries the date it was last reviewed at the top of the page.