ESP8266 simulator, running in this tab

Yes, with no card and no account needed to try it.

Simulated WiFi, yes, and it says so. Your sketch uses the real Arduino calls and the board joins, fetches and serves. There is no radio and no 802.11 under it, and on a chip whose reason to exist is the radio, that is said first rather than last. Signed in, you can switch on real internet.

Three, on the same chip: the NodeMCU V1.0 above, the Wemos D1 mini and the ESP-01S. Each has a board page and a pinout page with its pins in GPIO numbers.

Because D4 is GPIO 2 on this board. The silkscreen names are not GPIO numbers, and the runtime defines D0 to D8 so you can write the name you are looking at.

Yes. Edit the sketch and press Run: it compiles in the tab with clang for Xtensa, and the build panel shows every step. Nothing is uploaded.

The pin is: ten bits of the real voltage, behind the NodeMCU’s own 220k/100k divider, so the header reads to about 3.2 V. The registers behind it are this model’s own, because Espressif never published the chip’s, which makes analogRead the one call here you would have to change for real hardware, and the contract says so.

No. The editor, the templates, the gallery, the compiler and Run all work without signing in. Your browser keeps your work as you go. An account saves your projects online, so they follow you to any computer. It also gives you a link to share.

Forty-five, all on the free plan. Arduino: the Uno R3, Uno R4 Minima and Uno R4 WiFi, Nano, Nano ESP32, Nano RP2040 Connect, Mega 2560, Leonardo, Micro, the Pro Mini in its 5 V and 3.3 V builds, and the SparkFun Pro Micro. ESP32: the classic DevKit V1, the ESP32-S3, the ESP32-C3 and C6 DevKits, the Espressif DevKitC V4, the Freenove ESP32-WROVER, the Wemos LOLIN32 Lite, the Wemos D1 R32, the Cheap Yellow Display, the TTGO T-Display, the ESP32-C3 SuperMini and the Seeed XIAO ESP32-C3, C6 and S3. ESP8266: the NodeMCU, the Wemos D1 mini and the ESP-01S. Also the Raspberry Pi Pico and Pico W, the Seeed XIAO RP2040, the Waveshare RP2040-Zero, the Seeed XIAO SAMD21, the WCH CH32V003, the STM32F411 Black Pill, the STM32 Nucleo-F411RE and the STM32F103 Blue Pill, the BBC micro:bit V2, and the ATtiny85 and the ATmega328P in its 16 MHz and 8 MHz builds, which plug straight into the breadboard as bare chips. Your own code compiles in the browser for all of them. Then the Raspberry Pi 4, Pi 5 and Zero 2 W computers, which run your Python with gpiozero and RPi.GPIO, with nothing to compile. Each board page lists what it can and can’t do. For example, the WiFi boards have pretend WiFi, not a real radio, and the page says so.

Yes. A real compiler (clang, built for the web) runs in your browser. It downloads once, and your browser keeps a copy. After that, every build happens on your own computer. There is no build server and no waiting in line, so there are no build minutes to run out of.

Any up-to-date Chrome, Edge, Firefox or Safari, on a computer, a phone or a tablet. They all support WebAssembly, which Mokxi needs, and they have for years.

Yes. The editor works with touch, the buttons are big enough to tap, and the layout fits a small screen. The simulation runs on the phone itself.

Yes. Every account can try Pro free for 7 days, once. It takes a card, nothing is charged for those days, and if you cancel before they end you pay nothing. It starts when you choose it.

Yes, in one press from your account page. Your plan runs to the end of what you paid for.

Yes, once per account. Write to us within 14 days of a payment and we refund all of it. Lifetime Pro is refunded in full within 14 days of buying it.

Yes. Students get Pro at half price with a school email.

No. The simulator works signed out, so your class starts from one link with nothing to sign up for. An account only adds cloud saving and sharing, and a student can make one later, or never.

Yes. Everything runs on the machine in front of the student, so a Chromebook works as well as a lab PC.

Nothing, if your students only need to open and run circuits: the whole simulator is on the free plan. The class tools (a roster, starter projects, auto-graded checks, the gradebook) come with Pro and Classroom. Classroom is $9.99 a student a year, from 5 students, so at least $49.95 for the year. Your own seat is free, and from 50 students each one costs less. Your students get Pro’s room while they are in your classes. Pay by card, invoice or purchase order. Pro on its own runs classes for up to 10 students in all. To try the class tools with real students first, start the free 30-day trial from your class page: one class of up to 20 students, no card.

Yes. A student’s projects in a class are always private: they cannot be opened by link or put in the gallery. One exception, and only for reading: a teacher may open, and never write, a project owned by somebody in a class they teach, which is what a card on the class wall does. What we store about a student, who processes it, how a school has it deleted, and how we handle COPPA consent for students under 13 and FERPA as a school official are all on the student data privacy page at /privacy/students.

Every signed-in account gets questions every day: 5 on a free account, 50 on the Pro trial, 100 on Pro and the other paid plans, and 25 on Lifetime Pro.

Yes. It knows which board the project is on and answers for that board, from an Uno to an ESP32, an ESP8266, a Pico or an STM32.

No. It proposes a change as a card. Accept is yours, and only appears once the changed code compiles; Ctrl+Z undoes it.

Your project text, the matching help articles and the last six messages of the chat, never your name or account. "What is sent" shows exactly what went.