Esp-01 Datasheet May 2026

Pro Tip: Keep a PDF of the ESP8266EX Technical Reference Manual on your desktop. You won't read all of it, but you will search for "Deep Sleep" and "GPIO" a thousand times.

Note: GPIO 15 (TXD) must always be LOW during boot. This is why you can't just plug this into a USB-Serial adapter without a button circuit. The datasheet makes the ESP-01 look limited (only 2 usable I/O pins, needs level shifting, awkward boot sequence). And honestly, for a new project, you should probably buy an ESP32-C3 or an ESP8266 D1 Mini. esp-01 datasheet

It’s a finicky, low-pin-count, voltage-sensitive pain in the neck. But when you finally get that "Hello World" printed over Wi-Fi from a board the size of a postage stamp, you’ll understand why this little blue module became a legend. Pro Tip: Keep a PDF of the ESP8266EX

| Mode | GPIO 0 | GPIO 2 | GPIO 15 (TXD) | | :--- | :--- | :--- | :--- | | | LOW | HIGH | LOW | | Flash Boot (Run Code) | HIGH | HIGH | LOW | This is why you can't just plug this

If you’ve been in the IoT hobbyist space for more than five minutes, you’ve likely seen the tiny, unassuming blue board called the ESP-01 . It’s the gateway drug to Wi-Fi-enabled projects, often costing less than a cup of coffee.