Why your Shopify size filter shows sizes that are sold out

Why does a Shopify size filter ignore stock?

Availability feels like a product setting: a shoe is in stock or it isn't. Shopify doesn't file it that way. It tracks stock for each size and color, and the size filter reads sizes the same way.

So a size filter on its own asks one question: does this product come in size 8? A sold-out size 8 still answers yes. Tick a second filter, and a product has to match both. In stock is that second question, and nothing asks it until the shopper ticks the box.

Tick both, and Shopify checks the exact size the shopper picked. A shoe whose size 8 is sold out drops out of the results. A size with nothing left in stock in the collection counts zero, and the Empty values section in Search & Discovery's settings can hide it or move it to the end of the list. On 2026-09-15 we ran that test on a public store using Search & Discovery, without changing anything there. One size returned three products alone and two with In stock ticked, and the product that left was sold out in that size.

Three traps inside Shopify's own filter

Out of stock doesn't mean sold out. The Out of stock value returns any product with at least one size or color sold out. A tee in stock in every size but XS shows under Out of stock and under In stock at once. On the store we tested, four of the eight products under Out of stock still had other sizes or colors to sell.

Continue selling counts as in stock. A size set to Continue selling when out of stock can still be bought at zero, so a size on pre-order stays in the filter. That's right while you take pre-orders. It's wrong when the box was ticked by accident and never unticked.

A size filter built on tags can't see stock. Tags and details saved on the whole product describe the product, not one size. Pair a size-8 tag with In stock and Shopify only checks that the shoe has some size in stock. In stock can check the size only when sizes come from the product's Size option, a size detail saved on each size, or Shopify's Shoe size category field linked to that option.

Four fixes, and what each one costs

All four fixes below assume filters already work on your theme. The Dawn and Horizon walkthroughs cover that part.

Pre-tick In stock from the menu. Open each collection on your store, tick In stock, copy the address from your browser, and paste it as that collection's link in your menu. Shoppers arrive with In stock ticked, so the first size they pick checks stock. The cost: fully sold-out products disappear from that first view too, and a shopper can untick the box. Anyone landing from Google, or from an ad that points at the normal collection link, skips the menu and gets the unfiltered page.

Pay a developer to tick it for the shopper. A developer can make your theme tick In stock whenever a size is picked. You pay for their time, and a theme update drops the change when it clashes with the new version, so check it after every update. A quick version can also miss shoe sizes that come from Shopify's Shoe size category field.

Move a tag-based size filter onto the Size option. In Search & Discovery, add a filter whose source is the Size option, or a size detail saved on each size, and delete the tag filter. Shoppers see the same sizes, and In stock can check them, but only once it is ticked.

Build the collection from in-stock sizes. Since July 2026, a collection can use Variants instead of Products as its source, meaning only the sizes and colors that match a condition such as Inventory stock is greater than 0. Filters on that collection then offer only the sizes it includes, so the size filter skips sold-out sizes without In stock ticked. The cost: a product sold out in every size leaves the collection, a store can have at most 100 collections built this way, and a size on pre-order at zero stock drops out too. The Variants option is new, so test a sold-out size on one collection before you rebuild the rest.

One setting looks related and isn't. Search & Discovery's Out-of-stock products option hides sold-out products or lists them last in search results and in the suggestions that drop down as shoppers type, not on collection pages.

Can a size filter check stock without In stock ticked?

Sledge is a Shopify filter and search app that can check stock inside the size filter itself. In the display settings for Sledge filters, the switch Show out of stock variant filter items ships turned on. Switch it off, and a Size: M filter returns only products that still have M in stock. The size list offers only sizes with stock behind them. Nobody ticks In stock, and nothing needs redoing after a theme update. The count beside each size follows the same stock rule as the results.

Sledge counts a size as in stock whenever Shopify lets shoppers buy it, so pre-order and continue-selling sizes still count, as they do in Shopify. Sledge also checks size and color separately. Pick Red and M, and a product whose Red M is sold out can still appear while other Red sizes and other M colors are in stock. Sizes saved as tags or as a detail on the whole product can't be checked size by size here either.

Fully sold-out products have two settings of their own in Sledge: one hides them, one moves them below everything in stock. The sort guide compares the two. The filter comes with every paid plan, from Pro at $29.99 a month after a 14-day free trial.

Shopify alone, a free fix, or Sledge?

If sizes rarely sell out, the menu link is enough and costs nothing. If a kids range turns over every week, the filter should check stock without asking the shopper to.