DigiSim Logic LabBuild the whole computer, not just the gates
A digital-logic workbench with 60 components: wire your first AND gate, then keep going until an 8-bit CPU runs assembly you wrote. In your browser, free to start.
Free to start · no login · runs in your browser
What you'll build
Real circuits from the template library — each one loads live, right here on this page.
What you open
The Logic Lab is a full editor: drag components from the palette, wire pins, and an event-driven engine simulates every signal — propagation delays, tri-state buses, contention and all.
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60 components
From AND gates and flip-flops to registers, RAM, ROM, an 8-bit ALU and a program counter.
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See every signal
Single- and 8-channel oscilloscopes, 7-segment displays and a 16×16 pixel screen.
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Write real assembly
Load programs into ROM with the assembly editor and watch your CPU fetch, decode and execute them.
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Yours to keep
Autosaves locally with no account. Export PNG/SVG images or .digi files, share circuits by link.
Learn the stack, not just the gates
Narrated SimCast lessons walk the same climb — and every lesson stays a live simulator, so you can pause anywhere and probe. The journal covers the theory.
69 narrated lessons in 7 languages Explore SimCast lessons
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Digital Logic Roadmap: From Gates to CPU in 30 Days
A day-by-day digital logic curriculum: 30 days of focused lessons, one blog post and one interactive template per day, from AND gates to a working CPU.
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Mastering the 4-Bit Register: Building Block of CPU Memory
A 4-bit register is four D flip-flops sharing a clock, storing a nibble each rising edge. Add a load-enable mux to get the storage cell behind every CPU.
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Program Counter Explained: The CPU's Bookmark
How the program counter tracks the next instruction, increments automatically, and gets overwritten by branches and jumps inside every CPU.
Free to start. One payment for the summit.
The free tier is a real workbench — Pro is one payment, not a subscription.
Free
$0- 16 components — gates, latches, displays
- 21 narrated lessons
- Local autosave, no account needed
- Share a few circuits by link
Pro
$32 one-time- All 60 components — incl. RAM, ROM, ALU and CPU blocks
- All 69 narrated lessons
- 250 cloud saves + year-long share links
- One-time purchase, no subscription
Academic emails get an automatic discount at checkout.
Questions, answered
What's in the free tier, exactly?
A real workbench: the core gates, latches and displays, the starter narrated lessons, and local autosave with no account. Pro adds the CPU-side components — registers, RAM, ROM, the 8-bit ALU — plus the full lesson catalog, as a single one-time purchase.
Is it really simulating, or just animating?
Really simulating: an event-driven engine with per-component propagation delays, tri-state/high-Z pins and bus-contention detection. Put the oscilloscope on any wire and read the actual timing.
Can I really program a CPU in it?
Yes. Build or open an 8-bit CPU, write assembly in the ROM loader, and watch fetch–decode–execute run live — all the way to a 16×16 pixel-screen output.
Classroom use? Refunds?
The free tier and all circuit embeds need no student accounts, and academic emails get an automatic discount. The Pro purchase is covered by our standard refund policy. Refund policy
The summit is a machine you built
Open the Lab and wire your first gate — the CPU is the same climb, continued.
Open the Logic Lab Or start from the physics — DigiSim Relay Lab