OfferUp has lots of ways to classify the items you're trying to sell. Items can only be posted in one category, so try to pick the best option. Users are not able to create additional categories.
Note: Posting items multiple times to have them show in multiple categories is not allowed.
From the Web
When browsing items from the web, all posting categories will be searchable from the category view on the left-hand side of the screen. Seasonal categories will not visible but any items in those categories are searchable by positing keywords.
From the app
When browsing items from the app, all posting categories except for Pet Supplies is searchable from the browse (house icon). Items in that category will be searchable by posting keywords.
Certain categories are temporary and cycle in throughout the year. Those categories won't show up as options when posting but items will show up in them based on keywords in the title and description.
Examples: wedding, exercise, spring, summer, halloween, back-to-school, brand new, holiday
Finding Your Items
You can find your posted items at any time by view your public profile page or your 'Selling' tab.
To locate your items from the search view, be sure you're looking in the right area and using appropriate keywords (i.e. your username and/or the words in your description or title).
Items are sorted by a number of factors including: distance, time posted, and popularity. Although your items may not be visible in the ‘Popular near Me’ or ‘Search Everything’ feed, they will be in the category you posted them under and when relevant keywords are searched.
To view all your active items, tap the ‘Selling’ tab.