One of these is a window manager. The other is a card catalogue.

Kuadro asks nothing of you: no price, no account, no installer, no library format. Its own page says it is released as is, free for any use including commercial use, with the one restriction that you cannot redistribute it as your own, and the download is a single executable that needs no installation. If what you want is four reference images pinned around the edges of a drawing app while you work, download it, and close this page — nothing below will make you happier than that will.

Coii Ref is $19 once, macOS 11 or later, three machines, thirty days to try it with no card and no account. It solves a different sentence: not keep this picture in front of me, but find the picture, out of forty thousand, that I half remember saving. Those two sentences describe the same afternoon and almost none of the same software, which is why this comparison is mostly a question about which half of your day is the annoying one.

The table

Marked from the reader's side, not ours. Rows Kuadro takes are Kuadro's.

Two of those rows deserve their weight said out loud. Kuadro is free and portable, and a tool you can run off a USB stick in a studio where you do not control the machines is a genuinely different category of useful. And Kuadro puts an image over the thing you are painting in, which Coii Ref does not do at all.

What Kuadro is better at

The price is zero and the licence is generous. Not free-for-personal-use, not free-with-a-nag: their page states free for any use, commercial included. For a student, or anyone kitting out a room of machines, that is not a rounding error against $19 — it is the difference between installing something and asking permission first.

It is a window manager for pictures, and that is a real job. Every image is its own borderless window. You drag them onto whichever monitor has room, snap them against each other, rotate with a modifier and an arrow key, desaturate, and hit a hotkey to bring one to the front. Then you save the arrangement as a layout and reopen it tomorrow. The version 0.9.5 notes on their page describe snapping between panels, pasting an image straight from the clipboard, and auto-saving the board so an arrangement is not lost. If you paint with three references at the edges of the screen, this is closer to what you meant than any library app is.

No installation, no state, no obligations. One executable. Layouts store image locations relative to the .ref file, which their own release notes describe, so a folder of references plus its layout can move to another drive or a memory stick together. Coii Ref writes a database, thumbnails and proxies into the folder you point it at, which is portable in its own way but is not the same trick.

Windows. Kuadro's primary build is a Windows one. Coii Ref does not run on Windows and no page here will pretend otherwise. If half your studio is on PCs, that ends the discussion for the studio.

The thing to check before you rely on the Mac build

The Kuadro page offers a Mac download, and the Gumroad listing for it is Kuadro OSX 0.9.5, priced at nothing. The listing's own note from the developer says the OSX version is officially unsupported, that 0.9.5 is left up for those who want to try it, and that they hope to resolve the OSX issues in a future release. The newest entry on the site's own What's New list is 0.9.5, whose Mac line is that it was updated to work on OSX High Sierra.

That is the whole of what is checkable, and it is worth knowing before you build a habit on it rather than after. It is not a verdict on the software: plenty of people run it happily, the licence costs nothing, and a tool that does one thing can be finished. Try it on your own Mac, on your own macOS version, and let that answer the question rather than anybody's page about it.

What Coii Ref is better at

Finding something you did not label.

A layout holds the images you chose this morning. It does not help at all with the folder of eleven thousand you have chosen from over four years — and that folder is the actual problem in most reference habits. Coii Ref indexes the folders where those files already sit and gives you one line to interrogate them:

AND across keys, OR inside a comma list. type:video ext:mov narrows to clips, has:notes no:tags finds the ones you wrote about but never filed, width:>=3000 finds what will hold up printed. A term the parser does not recognise becomes free text instead of an error, so the grid keeps returning rows while you are still typing. Save the string as a view and it is re-parsed every time you open it, which means renaming a tag updates the view instead of breaking it.

Tags, ratings and notes that live somewhere. Kuadro shows you a file. Coii Ref knows things about a file: what you rated it, what you tagged it, what you wrote on it at two in the morning, what its dimensions and EXIF say. That is the substrate a search needs and a viewer has no reason to keep.

Video, treated the same as everything else. Same index pass, same tags and ratings, same query line, proxies written at canvas resolution so a board of clips scrolls like a board of stills. For anyone collecting film frames and the shots they came from, this is not a feature list item, it is most of the library.

A board is a file you can read.

A .coii-canvas is plain JSON, saved wherever you put it, listing which images sit where. It diffs in git, syncs through whatever you already sync with, and survives you changing your mind about applications in three years. This is the one claim on this site you can verify with cat rather than trust, which is why every page here eventually reaches it — see the case for keeping a board as a file, where a competitor genuinely wins the same argument.

A watcher, so the library does not go stale. Rename a folder in Finder, move a drive, drop in three hundred new frames: filesystem events turn into the smallest re-scan that makes the index true again. There is nothing to re-import and nothing to remember to do. It keeps running after the trial ends, so an unpaid copy still tells you the truth about your disk.

Running both, which is what most people should do

These tools do not compete for the same minute, so the sensible arrangement is not a choice at all. Use Coii Ref to find the eight images, drag them onto a canvas, and use Kuadro — or PureRef, which does the floating job with more polish and is free for personal use — to hover the two you actually paint from.

Nothing about that costs you anything on either side. Coii Ref never copies, moves or renames a file, so Kuadro opens the same originals afterwards and any layout you already saved still resolves. It is not a migration, because there is nothing to migrate: your files are your files, and the app that indexes them writes only beside them.

What switching actually costs

If you decide to stop using Kuadro entirely, the cost is an hour and one decision.

The hour is the first index. You point Coii Ref at the folder your references already live in, and it reads dimensions, EXIF and colour, writing thumbnails and canvas-resolution proxies inside that folder. Nothing is copied out, and nothing is renamed. On a large library you start it and go and do something else.

The decision is what to do with your .ref layouts. Coii Ref cannot open one — its only importer reads a refern library, and no page here will imply otherwise — so an arrangement you care about gets rebuilt once on a canvas, or left where it is and opened in Kuadro when you want it. Rebuilding six images on a canvas takes about ninety seconds. Rebuilding forty layouts does not, and if you have forty, keep Kuadro.

What you gain immediately: every image you have ever saved becomes reachable from one line, instead of reachable if you remember which folder. What you lose immediately: the floating windows. Weigh those two honestly, because most of the disappointment in this category comes from someone buying the second kind of app while wanting the first.

Where the workspace lives, and why that is the row to read twice

A free tool and a paid one are easy to compare on price and hard to compare on what happens in year three. The row that decides that is not price; it is where each app keeps what it knows.

Kuadro keeps almost nothing, which is a legitimate answer: a .ref layout points at images with paths relative to itself, and everything else is the files you already had. Nothing to corrupt, nothing to export, nothing to lose beyond an arrangement. Coii Ref keeps considerably more — an index of every file it has read, thumbnails, canvas-resolution proxies, your tags, ratings and notes — and so it owes you an answer about where all of that sits.

The answer is that all of it goes inside the folder you pointed at. There is no application-support directory holding the part that matters, no library file somewhere in your home folder, and no account holding the tags. Copy the directory to an external drive and the whole workspace — index, thumbnails, proxies, canvases — arrives with it and opens on a Mac that has never seen it. Delete the three coii- items and you are back to plain folders of images with nothing missing, because nothing of yours was ever inside them.

This matters more for a $19 app than for a free one, and pointing that out is not a sales line. When you pay for something you take on a small risk that the thing you paid for stops being the thing you use. The mitigation this app offers is not a promise about the future; it is that the boards are plain JSON you can read today and the originals were never touched. Check it with cat during the trial and you never have to take our word for it again.

The trial, and what happens on day thirty-one

Kuadro has no trial because it has no price. Coii Ref's is thirty days, every feature, no card and no account — and the shape of the ending is unusual enough to be worth stating plainly, because it is the sort of thing people assume the worst about.

At day thirty-one one category of action stops: growing the library. You cannot register a new folder, run the importer, or kick off an indexing pass by hand until you buy. Everything that reads keeps working, permanently — search, saved views, tags, ratings, notes, canvases, thumbnails — and the folder watcher keeps running too, so a file you rename in Finder next spring does not quietly turn the index into a liar. An unpaid copy does not lock the door on work you already did. It just stops taking on more.

The purchase is $19 once, three machines, updates included, nothing renewing. There is no update check in the app because there is no in-app updater, and no analytics of any kind: the only outbound requests it ever makes are the licence check when you press Activate, and one at launch read only for its Date header so that a wound-back clock cannot mint free trial days. If you work somewhere that audits outbound traffic, that is a short list to defend, and it is the same list whether you have paid or not.

Two habits, and which app each one belongs to

Watch what you actually do for a week and one of these will describe it.

The first habit is look at this while I make that. You collect little, reuse often, and the images you need are the ones you chose in the last hour. The friction is screen real estate and window focus, not retrieval. Kuadro, PureRef and every other floating board exist for this habit and they are right to. A library app used this way is a heavier way to open four files.

The second habit is I know I have one of these somewhere. You save constantly, from everywhere, into folders that made sense at the time. The friction is that the collection has outgrown your memory of it — a scroll is not a search, and a folder tree is a guess about what future-you will look under. This is what an index is for, and it is what Coii Ref was built around: one string over everything, on files that never moved.

Most working artists have both habits and hit the second one about twice a week. That is the actual argument for owning a library app alongside a viewer, and it is worth exactly as much as the number of times a fortnight you go looking for something you know you saved.

Who should pick which

Pick Kuadro if:

• you work on Windows, or on machines you do not control;
• the job is holding four images in view while you draw, and that is genuinely the whole job;
• you would rather have a tool that costs nothing and does one thing;
• your reference collection is small enough that finding things has never been the annoying part.

Pick Coii Ref if:

• the collection is the problem: thousands of files, several drives, folders someone reorganises;
• you want tags, ratings, notes and one query line over all of it;
• half of what you collect is video and you would like it in the same index;
• you want the boards you compose to be files in your own folders rather than rows inside an app;
• you are on a Mac and want the app you rely on to be one that is currently maintained.

If you are weighing this against the bigger libraries rather than against a viewer, the honest comparisons are Coii Ref against refern, which is more capable than we are on almost every axis, and against Eagle, which copies what you import into its own library by design. If you want the free end of the shelf, BeeRef is open source and cross-platform, and Inboard is the other small Mac app in this space. And if you have never used anything and are wondering whether macOS already covers it, start with Finder tags — that page argues the free option's case properly before it argues ours.

Thirty days, every feature, no card and no account: download it and point it at the folder you are most embarrassed by.