A library you actually use.

A collection is a folder for saved items. The same item can belong to many. The same collection can hold items of different kinds — articles next to videos next to podcasts. The structure exists for one reason: so that a year from now, when you can’t remember the title but you remember why you saved it, you can still find it.

How they behave

Three properties to keep in mind.

— Membership is a set, not a path. An item is in a collection or it isn’t. Removing it from one collection doesn’t remove it from the others. An article you saved into Reading and Long-form and 2026 sits in all three; clearing Reading leaves it in Long-form and 2026.

— The root is implicit. Saves land in your library without a default collection. Items not assigned to any explicit collection still appear in the popup under All.

— Renaming a collection doesn’t break links. Collections are stored by ID, not by name. Rename freely.

Nesting

Free readers can nest collections one level deep: Reading → Long-form, but not Reading → Long-form → 2026. Pro readers can nest up to five levels.

The depth limit exists because, past a point, a deeper folder tree is worse at retrieval than a flatter one with more tags. Five is a generous ceiling — most readers settle on two or three.

In the popup, the chip row is a single-level slice of the tree. Tap a collection chip and the popup drills down to that collection; a ← back arrow appears in the breadcrumb pill to step up one level. The breadcrumb in the popup header tells you where you are.

How to assign a collection on save

There are three ways. The fastest is the default collection per destination: if you’ve configured Markdown → Reading and Notion → Inbox, every save lands in those collections automatically. Override on save by opening the popup before pressing Alt + S and picking a different chip.

After-the-fact, the popup row has an Add to… action. The full Options page has a multi-select assignment UI for moving many items at once.

Smart Rules (Pro)

Smart Rules are a Pro-only feature. A Smart Rule is a condition → action that runs the moment a save lands in the library. If the hostname contains youtube.com, add it to Watch later. If the title contains “review”, add the tag reviews. If the kind equals podcast, add it to Audio.

Rules can do two things, both additive: add a tag or add the item to a collection. They cannot send notifications, fetch external data, modify other items, or remove tags — by design.

Open Smart Rules in the Options page. Add a rule. Each condition picks a field (hostname, url, title, kind) and an operator (equals, contains, startsWith, endsWith). A rule with multiple conditions can be set to match all of them (AND) or any of them (OR) via the rule’s condition logic.

Rules are scoped to this device. They are not synced. To replicate a setup on another machine, recreate the rule there.

Notion routing falls out of the collection action: if a rule adds the item to a collection that has a Notion database mapping, the export will use that database. See Pro features → Multi-database Notion routing.

A note on tags vs. collections

If the question “tag or collection?” comes up, here’s the working answer: collections are for retrieval, tags are for filtering. A collection is a destination the item will live in. A tag is a property the item carries. Collections nest; tags don’t.

That said: nothing forces this distinction. Shelf doesn’t penalise overlap. If you find yourself making a tag and a collection with the same name, pick whichever feels lighter and stop second-guessing.