At work we make websites for other companies. One of our client wanted us to make a e-commerce website for them. Nothing out of the ordinary until we realized they had 50 000+ products to sell and their classification is inexistant. In other words, we don't have ay categories to work with. They just told us to "Put a search bar and it'll be fine".

So, how would you make an e-commerce site work for the users without any kind of browsing through lists of products ? 

**EDIT**
The client is a reseller. He sells power outlets, light bulbs, electrical cords and stuff like that. The reselling part is why he doesn't have categories, because every single seller manage their own database with their own description for each product.
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I would recommend a [masonry-like](http://masonry.desandro.com/) experience as Pinterest implements. Infinite scrolling of all 50k products and have a details page for each one. Keep track of which products are viewed the most on a weekly basis and display those towards the top.

It sounds like this client wants an adventure-like experience with a search bar that searches on just one field; product name.

That is my 1/50th of a dollar; 2 cents =)
Your client might not be able to assign categories to products, but there is noting stopping them assigning categories to *sellers*. 

The kind of sellers using a resale ecommerce site are likely to be specialists in certain categories already, rather than having a diverse range of products (e.g. there will likely be sellers that specialise in lightbulbs and related items). You could build loose categories around this information to augment the search functionality. For example you could have an option to "view more sellers like this", or "view all items from similar sellers".