What can Shader Desk do without an account?

Everything except the review lanes. The shader is compiled by your own GPU driver and the diagnostics are shown against your line numbers; if it compiles it renders live with the Shadertoy uniform set; the declaration inventory, the per-pixel cost profile, the twenty-eight GX lint rules, the portability matrix, the deterministic GLSL ES 1.00 to 3.00 translation and the CSV and Markdown exports are all free, with no account and no run.

Why does my Shadertoy shader not compile in my own page?

Almost always three things at once, and Shader Desk names all three before you run anything. Shadertoy injects a uniform block you never see - iResolution, iTime, iMouse and the iChannel samplers - so a bare copy references undeclared identifiers. It injects a default float precision statement, without which a GLSL ES fragment shader will not compile at all. And it calls mainImage for you, where every other host only ever calls main. The reader raises GX-005, GX-026 and GX-027 for exactly these, and the port lane writes the wrapper and the glue.

Is the compile real, or is it a simulation?

It is real. The source is handed to WebGL's compileShader on your machine and the log comes back from your GPU vendor's own GLSL compiler, which is why the answer can differ between two browsers on two machines. The program is linked as well, and the uniforms the driver kept after optimisation are listed - a uniform that is declared but absent from that list is one your host code will look up and get null for.

Can a guest run a lane?

No. Running a lane is metered and this app does not sponsor guest runs, so a lane that is not a bundled replay needs a signed-in SkillSafe account. The exception is the bundled examples: the raymarcher replays the Explain, Optimize and Port lanes and the half-ported post effect replays the Diagnose lane, in full, without signing in and without spending a credit.

Does my shader get uploaded?

Not until you run a lane. The compile, the render, the parse, the cost model, the translation and every export happen in your browser. When you do run a lane, the source is sent for that one review and nothing about it is stored anywhere except your own SkillSafe account history.

What are the four lanes?

Diagnose accounts for every compiler diagnostic and hands back a patched source with an honest still-open list. Explain names the technique, spells out the coordinate space, walks the source section by section and lists the numbers worth turning. Optimize prices the per-pixel work against the browser's own counts and ranks the savings, each with before and after GLSL and a note on whether the image changes. Port moves the shader into a three.js ShaderMaterial with the uniform map, the host glue and the behavioural caveats the renames hide.

What is the reconciliation panel for?

It is what makes the paid lane accountable to the free one. Every flag the browser measured is sent to the reviewer as a fact it must answer, and the panel shows the answer flag by flag. A flag the reviewer handled shows its reasoning; a flag it declined shows the stated reason; a flag it never mentioned is rendered as unreviewed rather than quietly treated as cleared.

Shader Desk — compile your GLSL shader for real, then fix, explain, optimize and port it

Why will this shader not compile, and what is the fix?

Every driver diagnostic accounted for.

The shader

Drop a .glsl, .frag, .vert or .fs file here, or click to choose one. It is read in this browser.

Optional: the paired vertex shader, and what you are after

Vertex shader (optional) Where does it have to run? What do you see, or what do you want?

What this browser read reading…

The compiler log —

This is your own GPU vendor's GLSL compiler, not a simulation. Line numbers are corrected back to your source where a Shadertoy wrapper was added.

Running it

Resolution

What it declares

What it costs per pixel

Flags raised 0

Each one is sent to the reviewer as a fact it has to answer, and the answer comes back in the reconciliation panel below the result.

Translate the dialect — free, and deterministic

Translate to

Working

Checks

Findings

Next steps

Take it with you

The raw reply

The reply could not be read as the JSON contract, so it is shown exactly as it arrived rather than hidden.

Your recent runs

Saved to your SkillSafe account and mirrored in this browser, so they follow you to another device.

How this result was produced

Your shader was compiled by this machine's own GLSL driver and read as text in this browser first. Everything that read measured was sent to the reviewer as facts it had to reconcile, one flag at a time, and the reconciliation is shown above. Nothing about your shader is stored anywhere except your own SkillSafe account history.

Your shader, compiled by your own GPU before anyone reviews it