User Guide

This guide walks you through categor.io step by step. You need no technical knowledge. Each part builds on the one before, so it helps to read them in order the first time. If you have an account, try each step as you go.

• The idea: categories instead of folders
• Part 1: Exploring, no account needed
• Part 2: Your own things
• Part 3: Sharing
• Part 4: Receiving
• Part 5: Your store as a whole
• Part 6: Pictures and the console
• Good to know
• Words used on the site

The idea: categories instead of folders

On a computer you keep files in folders, and each file sits in exactly one folder. That forces a choice. Does the plane ticket for your summer trip go in Travel, in Japan, or in Receipts? Whichever you pick, you'll one day look for it in another.

categor.io is built on OntoDAG, which works differently. There are no folders, only categories, and anything can sit in as many categories as it belongs to. The plane ticket can be under Japan trip and under receipts at the same time. It's still one ticket, not three copies.

Categories sit inside other categories too. Japan trip can be under Travel. When you look at Travel, you see everything below it, however deep: the trip, and the ticket inside the trip, even though you never filed the ticket under Travel yourself.

One word matters throughout this guide: below. If A is below B, then A is part of B, or a kind of B. A dog is below animal. Your ticket is below Japan trip, which is below Travel. Everything on this site, sharing included, comes down to what is below what.

Part 1: Exploring, no account needed

Everyone can explore the public vocabulary: thousands of everyday categories, from toaster to photosynthesis, already arranged for you. They come in packs, collections on one subject.

Step 1: Open a pack

On the home page you see a list of packs. core holds everyday things (objects, people, places, events, documents). The others cover one field each, such as physics, medicine, geography or economics.

Click core. You see its top categories, such as physical-object, information, event and place. The small grey number next to a category tells you how many categories are below it.

Step 2: Walk up and down

Click physical-object, then artifact, then device. Each page shows:

• the category's name at the top;
• "under …": the categories it sits in. Click one to go up a level;
• the list below: the categories inside it. Click one to go down.

Now look for a category with two parents. Many things belong in more than one place, and the "under" line shows all of them.

The Home link at the top of every page takes you back to the start.

Step 3: See everything below, and narrow it down

At the bottom of a category's list you may see a link such as All 1,203 below device →. It lists everything below the category, however deep.

Above that list you'll find Narrow by, a row of suggestions, each with a number. Click one, say kitchen-appliance, and the list shrinks to things that are both devices and kitchen appliances. The number told you in advance how many would remain. Only suggestions that actually narrow the list are offered.

The heading now reads device and kitchen-appliance. Click the × beside either word to drop it again.

Step 4: Search

Type part of a name, such as toast, into Find a category at the top of any page, and press Enter.

Part 2: Your own things

Step 5: Create an account

Click Sign in, then Create an account. Choose a username with 3 to 32 letters, digits, dots, dashes or underscores, and a password of at least 8 characters.

Your username gives you an address, such as ada@categor.io. It looks like an email address, and works a little like one: people who know it can share things with you (Part 4). Nobody else can take your username, ever, even if you leave.

Everything you create is kept in your store. It is private: nobody else can see anything in it unless you share it.

Step 6: Add your first categories

Your Home page has a box called Add a category on the right. Type hobby as the name, leave Under empty, and click Add. Do the same for work.

These are now on your home page under Yours. Many people start with a few big areas of life like these, one for each "side" of themselves.

Step 7: File something under the public vocabulary

Say you have a dog called Rex. Add a category named rex, and in Under type dog. As you type, the site suggests names; pick dog.

Rex is now below dog, and so also below mammal, animal and organism: the public vocabulary already knows where dogs belong. Try searching for animal and clicking All … below animal. Rex is in the list.

Rex is still yours alone. Other people who look at dog see only the public categories, never your Rex. Filing something under a public category describes it for you; it doesn't publish it.

Step 8: Put one thing in several places

Open rex (click it, or search for it). On the right, under File rex under, type hobby and click File. The "under" line now reads dog, hobby. Rex is in both, and still just one Rex.

Step 9: Build inside your categories

Open hobby. Use Add a category under this to add photos, then open photos and add summer-2026 under it.

A handy trick for dates: in Under you can type a date category such as time(2026-08) for August 2026. Later, looking at time(2026) shows everything you filed anywhere in 2026, without your ever filing it under the year.

Step 10: Change your mind

• Take something out of one place. On its page, under Take out from under, click the × on the category it should leave. It stays in its other places. (home × takes it off your home page.)
• Remove a category. Open Remove … at the bottom right. The category goes, but the things under it are not lost: they move up to its parents.
• Undo. Click Store at the top of the page. Undo takes back your last change, and Redo puts it back again. The History list shows every change you've made.

Part 3: Sharing

Step 11: Share a category with someone

Say your friend Bob has the address bob@categor.io, and you want him to see your holiday photos.

1. Open your photos category.
2. Under Share with, type bob (the full address works too) and click Share.

Bob now gets photos and everything below it: summer-2026, and anything you add there later. You don't need to share each photo. Filing a photo under photos is enough.

The page now says shared with @bob.

Check the spelling. If Bob's address is new in your store, the site reminds you to check it. The site never tells you whether an address exists, so that nobody can use it to find out who has an account. A misspelled share simply reaches no one.

Step 12: What Bob sees, and what he doesn't

Bob sees photos and what is below it. He does not see:

• the other places you filed photos in. If it's also under your private family, family stays hidden;
• anything else in your store;
• the other people you've shared photos with.

And Bob sees nothing at all until he accepts you (Part 4).

Step 13: Groups

To share with several people at once, make a group. A group is just a category that you share with several people.

1. Add a category called climbing-club.
2. Share it with each member: bob, carol, dan.
3. File whatever the club should see under climbing-club.

Every member sees everything under climbing-club, and no member sees who else is in the group. Only you, the owner, see the member list.

Step 14: Groups inside groups (a company example)

Say Acme sets up its account like this:

• employees, shared with every employee;
• employee-information under employees, with the handbook under it;
• sales, shared with the sales team;
• sales-leads under sales.

Acme wants the sales team to see everything employees see as well. So Acme files employees under sales. Everyone in sales now sees the handbook, because it is below employees, which is below sales. Employees outside sales still don't see sales-leads.

This is the opposite of how you might first picture it. Remember that below means "part of": employees becomes part of what sales can see. More access means more below you.

On Acme's own pages, people who get something through a group are listed as through a group.

Step 15: Stop sharing

Open the category and click the × on the person's name under Take out from under.

If a change would stop someone seeing something, the site first shows a page headed This stops people seeing things. It lists who would lose what, and you choose Go ahead or Cancel. The same check runs when you take something out of a group or remove a category, so nobody loses access by accident.

Part 4: Receiving

Step 16: Requests

When someone shares with you for the first time, it doesn't appear straight away. Your home page shows a request instead: acme wants to share 3 things with you, with no content. That protects you from things you never asked for.

You have three choices:

• Accept. Pick where the sender should go in your store (at the top, or one of your categories, such as work), then click Accept.
• Block. You get no more requests from them, and nothing of theirs is shown.
• Leave it. The request stays until you decide.

The sender is never told what you chose.

Step 17: Where shared things appear

Once you've accepted Acme:

• On your home page, "Shared with you" lists Acme with the number of things it shares.
• Acme's page (click @acme) shows What acme shares with you and What you share with acme.
• Where you filed Acme, for example under work. Your work category then leads to everything Acme shares with you.
• Mixed into the vocabulary. If Acme's handbook is filed under the public document, you'll see it there too when you look at document, marked with a small acme label. Only you, and others Acme shared it with, see it there.

Shared things belong to their owner, so you can read them but not change them.

If you share something with someone yourself, you've accepted them too: their shares to you appear without a request.

Step 18: Blocking and unblocking

Open the person's page (click their name) and click Block …. To undo it, open the same page and click Unblock. Remove from your store goes further: you stop accepting their shares, and stop sharing with them.

Step 19: An address for one part of your life

You can have extra addresses, each tied to one of your categories. On your home page, under Your addresses, fill in New address, for one category: type work, choose your work category, and click Create. You now have ada+work@categor.io.

Anything shared with ada+work arrives in your work category. Give that address to colleagues, and keep ada for friends.

Each address has its own setting for requests. Open the address (click it under Your addresses) and choose under Requests at this address:

• shown: strangers can send you requests here;
• hidden: accepted senders only: only people you've already accepted can reach you here; others are silently ignored;
• as the account: follow the setting of your main address.

Requests are shown by default.

Part 5: Your store as a whole

Click Store at the top of any page.

• Export downloads your whole store as one file (ada.od). It's a plain text file in OntoDAG's own format, which you can keep as a backup. People who use OntoDAG's command-line tool, odag, can open it directly. Under Also include whole packs you can add complete packs to the file, for example all of biology to work with on your own computer. The packs you already use are listed first. This changes only the file, not your store.
• Import adds the contents of such a file to your store. First click Preview. You see what would be added, and whether the file would share anything with anyone, before anything changes. Then click Merge into my store, or cancel.
• History lists every change you've made, newest first, with Undo and Redo.

Part 6: Pictures and the console

Step 20: See a category as a picture

Below the name of every category are three links: List, Picture and As a command. Click Picture. The category appears in the middle, highlighted, with the categories it sits in on one side and the ones inside it on the other. Every box is a link, so you can walk around by clicking boxes.

A picture only ever shows what you can see yourself. On something shared with you, the owner's private categories don't appear, just as they don't appear in the list.

Step 21: Ask the same thing as a command

OntoDAG has its own short command language. The Console link at the top of every page opens it. Type a command after odag ▸ and click Run:

• get device kitchen-appliance lists what is both a device and a kitchen appliance;
• count animal says how many categories are below animal;
• below rex animal answers true or false: is Rex below animal?
• canon weight(3000g) shows how a value is stored: weight(3kg).

You don't need to learn this. Every page has an As a command link that opens the console with that page's question already typed in, so you can pick it up by looking.

When you're signed in, choose where commands run: Your store or Public vocabulary. In your store you can also change things:

• put holiday-photos adds a category, and put rex hobby files Rex under hobby;
• put photos bob@categor.io shares photos with Bob, exactly like the Share button;
• remove photos removes a category;
• undo takes back your last change, and history lists your changes;
• pack biology --show lists everything in the biology pack.

As on the pages, if a command would stop someone seeing something, the console asks first and waits for you to click Run anyway.

Some OntoDAG commands never run here, because they would read or write files on the site's computer or change its settings. The list below the console shows every command, and why any that can't run here are unavailable.

Good to know

Public words are public categories. If you add a category with a name the vocabulary already has, such as work, hobby or family, you get the public one. What you file under it is still private. On your own categories the site lists your things first; the public subcategories are behind a link such as 11 public categories under work.

Every pack is ready to use. You never need to add a pack before using it. File your things under gene or enzyme (biology), exoplanet (space) or antiviral (medicine) straight away, as with dog.

Nobody can search for you. The site never lists accounts. To share with someone you need their address, the way you need an email address.

Shares to addresses that don't exist go nowhere, for good. If you share with an address nobody has registered, it reaches no one. That stays true even if someone registers that name later: whatever was filed before they existed is never given to them.

Senders learn nothing about you. They can't see your store. They don't learn whether you accepted, blocked or ignored them.

Everything is undoable. Every change goes into your History, and Undo takes it back.

Words used on the site