Variants on ESP32 Overview

ESP32

Mon, 01 Jan 0001 00:00:00 +0000

Why it still matters

Ten years after launch, the original ESP32 is beaten on almost every individual specification by something newer in the family. It has no Wi-Fi 6, no BLE 5, no 802.15.4, the highest active current, and an instruction set Espressif has stopped designing new parts around.

It nonetheless remains a defensible choice, for three reasons that no newer part fully replaces.

It is the only ESP32 with Bluetooth Classic — specifically BR/EDR alongside LE 4.2. If your product needs to pair with a phone as an A2DP audio sink, act as a hands-free device, or talk to legacy Bluetooth serial equipment, the original ESP32 and the very new S31 are your only options in the family. Every part in between is Bluetooth LE only.

ESP32-C2

Mon, 01 Jan 0001 00:00:00 +0000

What it is for

The C2 exists to win price-driven design contests. If you are building a smart plug, a lamp controller or a Wi-Fi relay in six-figure volumes, the difference between a $1.00 chip and a $1.85 one is real money, and the C2’s job is to be the cheapest part that still speaks Wi-Fi and BLE 5.

Everything about it follows from that goal. The package is 4×4 mm, the smallest in the family. The core is a single RISC-V at 120 MHz — slower than the C3’s 160 MHz. SRAM is 272 KB. There are 14 GPIOs. And an unusually long list of peripherals simply is not present.

ESP32-C3

Mon, 01 Jan 0001 00:00:00 +0000

Why it is still recommended

The C3 was announced in 2020 as Espressif’s first RISC-V chip and its answer to the question “what replaces the ESP8266?”. Six years later it is neither the fastest, the most efficient nor the most featured part in the family — and it is still the one to recommend to most people building most things.

The argument is boring and correct: at $1.00 for the chip and $8 for the development board, with 400 KB of SRAM, a 160 MHz core, Wi-Fi, Bluetooth LE 5 and hardware ECC, the C3 has no gap between what it claims and what it delivers. Every framework supports it properly. Every tutorial works. The errata are known and worked around. Nothing about it will surprise you at integration time.

ESP32-C5

Mon, 01 Jan 0001 00:00:00 +0000

The one thing only it can do

“Why won’t my ESP32 connect to my Wi-Fi?” has, for a decade, had one overwhelmingly common answer: because the network is 5 GHz and every ESP32 radio was 2.4 GHz only. The C5 is the part that fixes this. It is the first — and as of now the only — Espressif SoC with a dual-band Wi-Fi 6 radio covering both 2.4 GHz and 5 GHz, with backward compatibility down to 802.11a/b/g/n/ac.

ESP32-C6

Mon, 01 Jan 0001 00:00:00 +0000

Why this is the default recommendation

The C6 is the chip that most new ESP32 designs should start with, and the reasoning is that it is the only part where nothing important is missing for a typical connected device.

It has the modern radio set: Wi-Fi 6, Bluetooth 5.3 with Mesh, and 802.15.4 for Thread and Zigbee — so it can be a Matter device over Wi-Fi or over Thread, a Zigbee node, or a bridge between them. It has a dedicated low-power core so sleep patterns can be sophisticated. It sleeps at 7 µA. It has 512 KB of SRAM, the joint-largest in the C-series. It has 30 GPIOs. And it has the strongest security certification of any chip in the family.

ESP32-C61

Mon, 01 Jan 0001 00:00:00 +0000

The proposition

The C61 is best understood as a cost-reduced C6. Same 160 MHz single RISC-V core, same Wi-Fi 6 on 2.4 GHz, same Bluetooth LE 5, same 30 GPIOs — for $1.46 instead of $1.85, with modules at $2.14 instead of $2.50.

What pays for the difference:

	ESP32-C6	ESP32-C61
802.15.4 (Thread, Zigbee)	Yes	No
Low-power core	20 MHz RISC-V	LP peripherals only
SRAM	512 KB	320 KB
Bluetooth	5.3 + Mesh	5
ADC channels	7	1
RMT	4 channels	None
In-package PSRAM	No (external only)	Up to 8 MB
Deep sleep	7 µA	~10 µA
Security certification	PSA Level 2	APM + PMP, no PSA L2
From	$1.85	$1.46

The trades are coherent for a specific kind of product: a mains-powered Wi-Fi device — an appliance controller, a Wi-Fi adapter, a POS terminal, a smart-home actuator — that benefits from Wi-Fi 6’s congestion behaviour but will never join a Thread network and does not need a coprocessor running during sleep.

ESP32-E22

Mon, 01 Jan 0001 00:00:00 +0000

A different kind of product

Every other chip on this site is a microcontroller you write firmware for. The E22 is not. It is a Radio Co-Processor (RCP): a self-contained networking subsystem that attaches to a host processor — typically running Linux — and presents itself as a network interface. The host runs the application; the E22 runs the entire Wi-Fi and Bluetooth stack.

This is a new product line for Espressif, announced in January 2026 and Wi-Fi 6E certified in June 2026. Strategically it moves the company from “cheap microcontrollers with radios” into competition with the connectivity silicon that goes into routers, set-top boxes and laptops.

ESP32-H2

Mon, 01 Jan 0001 00:00:00 +0000

Why remove Wi-Fi

Wi-Fi is expensive in every sense: die area, peak current, average current, and the RAM the stack consumes. A Wi-Fi transmission can draw a few hundred milliamps in bursts, and even an idle associated station must wake periodically to listen for beacons.

For a door sensor, a temperature probe or a light switch, none of that is wanted. What is wanted is a radio that can send twenty bytes, occasionally, using as little energy as possible, on a network that routes around dead nodes. That radio is IEEE 802.15.4 — the physical layer beneath both Thread and Zigbee — and the H2 is Espressif’s part built entirely around it.

ESP32-H21

Mon, 01 Jan 0001 00:00:00 +0000

What changed from the H2

The H21 is not a new architecture. It is the same basic proposition as the H2 — a 96 MHz single-core RISC-V part with Bluetooth LE and 802.15.4 and no Wi-Fi — with three targeted improvements aimed squarely at battery-powered mesh nodes.

An on-chip DC-DC converter. This is the most consequential change and the least visible on a specification sheet. Without it, the radio’s supply is derived through a linear regulator, and the difference between the battery voltage and the radio’s operating voltage is burned as heat. A switching converter recovers most of that. Espressif quotes roughly 8.2 mA during receive as a result.

ESP32-H4

Mon, 01 Jan 0001 00:00:00 +0000

Why it is more than an H2 refresh

The H2 and H21 are sensor-node chips: one slow core, 19 pins, minimal peripherals. The H4 keeps the H-series radio philosophy — 802.15.4 plus Bluetooth LE, no Wi-Fi — but scales everything else up enough to build a device rather than a sensor.

Two RISC-V cores instead of one, at 96 MHz, with a dedicated low-power domain for selected peripherals. Two cores in a mesh device is more useful than it sounds: the 802.15.4 stack and the Bluetooth stack are both timing-sensitive, and separating protocol work from application work removes a class of jitter problem.

ESP32-P4

Mon, 01 Jan 0001 00:00:00 +0000

The chip that gave up the radio

Every other part in this family is defined by its radio. The P4 is defined by not having one. There is no Wi-Fi, no Bluetooth, no 802.15.4 — and the die area, power budget and pin count that would have gone to a radio went into application performance and I/O instead.

The result is by some distance the most capable Espressif application processor:

ESP32-S2

Mon, 01 Jan 0001 00:00:00 +0000

Why it exists

The S2 was the first structural departure from the original ESP32, and its design brief was subtractive: remove Bluetooth entirely to cut die area, cost and power, then reinvest the savings in a native USB controller, more pins and more touch channels.

At the time that was a coherent proposition. A great many Wi-Fi products — smart plugs, panels, appliance controllers — never use Bluetooth for anything except initial provisioning, and provisioning can be done over a SoftAP instead. Paying for a Bluetooth radio you disable in firmware is waste.

ESP32-S3

Mon, 01 Jan 0001 00:00:00 +0000

Why it is the community favourite

If you look at what people actually build with ESP32 parts in 2026 — LVGL touchscreen dashboards, network cameras, voice assistants, e-paper displays, handheld gadgets — a large majority of it runs on an S3. The reason is that it is the only part in the family that is simultaneously fast enough, has enough memory, has enough pins, and has a radio.

ESP32-S31

Mon, 01 Jan 0001 00:00:00 +0000

What is new here

The S31 is the most significant single release in the family since the original ESP32, for two reasons.

It moves the S-series to RISC-V. The S2 and S3 used Xtensa LX7 cores. The S31 uses two 32-bit RISC-V application cores at up to 320 MHz — and unusually, adds an MMU, which the rest of the family lacks. Espressif quotes 6.86 CoreMark/MHz, and one of the two cores carries a 128-bit SIMD data path for signal processing and quantised inference. A separate 40 MHz low-power RISC-V core handles background work.