What’s new in AutomataVerse

A new Tests tool in the dock. List the strings your machine should accept and reject (or input and expected output for Mealy and Moore machines) and get a pass / fail table in one click, instead of running strings one by one.

A new Share tool in the dock creates a short link such as automataverse.com/m/c3ELnGde. Anyone can open it — no account needed — and it is not a picture: they get the machine in the simulator, fitted to their screen, and can type a string and run it. They cannot change what the link shows; “Edit a copy” gives them their own. You need to be signed in to create a link, and you can copy or delete your links from the same panel.

Every shared machine also comes with an <iframe> snippet, so a course page, a blog post or lecture notes can carry a live automaton that readers can run.

The PNG button in the dock is now Export, with two more formats. SVG is a vector drawing that stays sharp at any size and opens in Inkscape, Figma or Illustrator. TikZ gives you a tikzpicture for the automata library — states where you placed them, loops, bent edges, ε and z₀ typeset properly — ready to paste into a homework or a paper. Both are in ⌘K as well.

The new Convert tool in the dock opens a construction stage that works like the simulator itself: the same grid and run bar, with Play, step forward and back, speed, and a progress strip you can click. Your machine is on one side and the new one is built on the other — states pop in as they are discovered, each new transition is drawn with a travelling dot, the states in play light up, and a caption says what just happened. Arrow keys step, space plays, Esc closes. The result opens as a new machine next to your original.

The subset construction, ε-moves included. See which set of NFA states every DFA state stands for, with a trap state added when the NFA can get stuck.

Unreachable states fade out, states that still count as the same share a colour, and the colours split until only real differences remain — then each group merges into one state. If your DFA is already the smallest possible, it says so — a quick check for a hand-built answer.

Turns an ε-NFA into an ordinary NFA on the same states, showing the ε-closure of each state and the transitions that replace the ε-moves.

Type an expression such as (a+b)*abb and watch Thompson’s construction assemble the NFA fragment by fragment, drawn the way textbooks draw it. Or go the other way: any DFA or NFA becomes a regular expression as its states disappear one at a time and the edge labels grow into expressions before your eyes.

Type a context-free grammar — S -> aSb | ε — and get the PDA that accepts the same language, with each rule shown becoming a stack operation. Open it and watch the stacks as it runs.

“New” in the simulator now offers two things besides machines: a Regular expression tab, where the NFA is rebuilt step by step as you type, and a Grammar tab with two views — Derive (parse trees) and To PDA. They sit next to your machines, are saved like them, and “Open as a machine” puts the NFA or PDA they build into a machine tab of its own. Also in ⌘K.

Type a context-free grammar and a string, and watch a leftmost derivation grow the parse tree one rule at a time — the variable being rewritten in pink, the ones still waiting in violet, the finished string in green, and the derivation S ⇒ aSb ⇒ … written out underneath. It handles ε-rules and left recursion such as E -> E+T, and tells you plainly when the grammar cannot produce the string. If the grammar is ambiguous for that string you are told so and can flip through every parse tree: x+x*x under E -> E+E | E*E | x shows both (x+x)*x and x+(x*x).

Each construction has its own page with the same animated stage built in — press Play or expand it to full screen, type your own regular expression or grammar right in the run bar, and open the result in the simulator. Below it: the algorithm in four steps and answers to the usual questions.

Every page and the simulator itself were redrawn: a light, quiet layout with a new run bar, tool dock, state toolbar and stack panel. Pink now means one thing only — where the machine is right now.

The tape extends with blanks in both directions as the head moves, so a machine no longer stops just because it walked off the edge.

A DPDA can now take a transition without reading input, so the textbook constructions that pop the stack at the end of the string work as written.

A label the simulator cannot read is skipped and pointed out instead of crashing the run. Pushdown transitions are drawn one operation per line, which makes busy edges readable.

A machine file is checked before it is loaded. If something is wrong you are told what, rather than getting a half-loaded canvas.

Opening a submission to grade replaced the list of machines you had open in the simulator. Your machines now stay exactly as you left them.

A Turing machine that adds two binary numbers joins the bundled examples.

Teachers attach test cases to an assignment. Students never see them. Each submission is run against the tests and gets a suggested score, which the grader can apply or overrule.

Run the tests on every submission together, see “7/8 tests” next to each student, and apply the suggested scores to everything not yet graded.

Test cases can be changed once an assignment is live; results from the old tests are discarded so nothing stale is shown.

Teachers can share a public set of sample tests. They appear ready to run in the student’s Tests panel when the assignment is opened.

Upload a correct machine when you create an assignment, or later from Edit tests. It stays hidden from students. A submission that accepts exactly the same language gets full marks, even if it is built differently (an NFA against a DFA, more or fewer states). A wrong one comes back with the shortest string the two machines disagree on, and whether it was wrongly accepted or wrongly rejected. Works on its own or together with hidden tests.

Opening an assignment or a submission to grade could briefly show the machine from your last session instead, and Submit would then send that one. It now waits for the assignment to load first.

Pro subscriptions moved to a new payment provider, with upgrade and cancel handled inside the app.

In India, Pro is ₹499 a month and can be paid with UPI AutoPay or a card.

Outside India, Pro will be charged as $6 a month by card. Until international card payments are switched on, checkout everywhere is in rupees.

The simulator stays free. If it helped you through a course, the new Sponsor page lets you chip in any amount you like, once, in rupees or dollars, with no account needed — it goes to the servers, the domain and the time that keep the site running. There is a Sponsor button in the simulator, and people who use it regularly will see a small, dismissible note now and then; neither appears during an assignment.

A cancelled subscription now stops at the end of the period that was paid for. Some accounts had kept Pro after their subscription ran out; they are back on the free plan and can upgrade again at any time.

A new Story page, linked from the footer. It starts with a homework sheet that came back with a red circle and follows it, chapter by chapter, to the simulator you use today: why it runs entirely in your browser, what one late night with it looks like, and what it takes off a TA’s desk.

Keep several machines open side by side and switch between them like browser tabs.

Save a picture of your machine for notes, slides and homework.

Remove a single transition without deleting the states it connects.

Transition labels are read more reliably across all seven machine types.

An extra theme alongside light and dark.

Create an account with email or Google, with a profile and settings page.

Save machines to your account and open them from any device.

A daily streak and activity calendar to keep practice going.

Create a group, set assignments with instructions and a due date, and let students submit straight from the simulator.

Admins invite people by email and choose their role; invitations arrive in a notification bell.

Open a submission in the simulator, run it, then leave a score and feedback.

Invitations, membership and role changes are verified on the server, so only the right people can change who is in a group. (July 2026)

Building machines stays free. Pro adds cloud storage and larger classrooms, with a pricing page and subscription management in your profile.

Plain pages that say what is stored and why.

DFA, NFA, deterministic and non-deterministic pushdown automata, Turing machines, Mealy and Moore machines.

Add states, drag them around, draw transitions between them, mark accepting states, and pan and zoom the canvas.

Play a whole input string or advance one step at a time, with the active state and transition highlighted, the stack shown for pushdown automata and the tape for Turing machines.

Switch a Turing machine to two tapes, each with its own head.

A ready-made machine for every type, one click away, plus a Learn page that walks through them.

Reach every action from the keyboard.

Export a machine to a file and load it back later, or share it with a classmate.

Drag the control panels where you want them and pick the theme you prefer.