WLED & LED Glossary

An LED that contains a built-in integrated circuit (IC) allowing it to be individually controlled by a microcontroller. Each LED in a strip can display any colour independently, enabling animations and effects. Also called "smart LEDs" or "intelligent LEDs". Examples: WS2812B, SK6812, APA102.

An addressable LED chipset that uses a two-wire SPI protocol (data + clock) instead of the single-wire timing of WS2812B. The separate clock line enables much faster data rates (up to 20MHz+), eliminating flicker at all camera shutter speeds. The SK9822 is a widely available and nearly identical clone.

Access Point mode. When WLED cannot connect to a Wi-Fi network (or has no network configured), it creates its own Wi-Fi hotspot named "WLED-AP" so you can still reach the web interface. Default password is "wled1234". Navigate to 4.3.2.1 in a browser when connected to this hotspot.

American Wire Gauge. A standard scale for measuring wire conductor diameter. Counterintuitively, lower AWG numbers mean thicker wire with higher current capacity. AWG 22 is thinner than AWG 18. Common WLED build gauges: AWG 22–18 for power wires, AWG 24–22 for signal wires.

A secondary data wire present in WS2813 and WS2815 strips. If a single LED IC fails and cannot pass the data signal through, the next LED reads from the backup line instead, maintaining signal continuity. Standard WS2812B strips do not have this — one failed IC breaks all subsequent LEDs.

In WLED, a "bus" refers to a single LED data output from the controller — one GPIO pin driving one strip or strip segment. ESP32 boards can drive multiple buses simultaneously, enabling independent control of several strips from one controller.

The sequence in which a LED IC expects to receive red, green, and blue data. Most WS2812B LEDs use GRB (green first, then red, then blue) despite being marketed as RGB. If colours appear incorrect in WLED (e.g. red appears green), adjust the colour order in Config → LED Preferences. Common orders: GRB, RGB, BGR, RGBW.

A WLED feature that automatically reduces the overall brightness of all LEDs to prevent the total current draw from exceeding a set threshold. Configured in mA in Config → LED Preferences → Maximum Current. Essential for protecting your power supply from overcurrent.

A small electrolytic or ceramic capacitor (typically 100–1000µF, 6.3V or higher) placed across the +5V and GND terminals at the beginning of an LED strip. Absorbs voltage spikes from the inrush current when LEDs switch on, preventing LED IC damage and reducing flicker. Especially important for long wire runs.

The GPIO (General Purpose Input/Output) pin on the microcontroller that sends colour data to the LED strip. In WLED, this is configured in Config → LED Preferences. A 300–500Ω resistor should be placed in series between this pin and the strip’s data input to protect against signal reflections.

Data Out and Data In — the data signal connections on an addressable LED strip. The controller connects to DIN of the first LED. Each LED passes data through its IC to DOUT, which connects to the DIN of the next LED. Cutting between DIN and DOUT of a LED breaks the data chain for all subsequent LEDs.

A built-in animation pattern in WLED. Effects range from simple (Solid, Breathe, Blink) to complex particle simulations (Fire 2012, Fireworks) and audio-reactive visualisers. WLED 0.15 includes 180+ effects for 1D strips, with additional 2D effects for LED matrices.

A dual-core 240MHz microcontroller with built-in Wi-Fi and Bluetooth, made by Espressif. The preferred platform for WLED due to its processing power, ample GPIO pins, and multiple hardware SPI/I2S interfaces. Variants include the ESP32-S3 (more GPIO), ESP32-C3 (budget RISC-V), and ESP32-S2 (single-core, USB native). All support WLED.

A single-core Wi-Fi microcontroller, the predecessor to the ESP32. Supported by WLED but officially designated as legacy hardware. Limited RAM (80KB) restricts it to smaller LED counts and fewer features. The Wemos D1 Mini and NodeMCU V2 are popular ESP8266 development boards.

A safety device installed in the positive wire between the power supply and LED system. When current exceeds the fuse rating, it melts and breaks the circuit — protecting against wire fires from short circuits or faults. Automotive blade fuses in a fuse holder are the most common type used in LED builds. Always fuse your positive wire.

The number of times per second WLED updates the LED strip with new colour data. Higher FPS means smoother animations. Constrained by LED chipset speed (WS2812B maxes around 60fps at 300 LEDs), strip length, and controller processing. Set in Config → LED Preferences → Target FPS.

General Purpose Input/Output. The programmable pins on a microcontroller that can be configured as digital inputs or outputs. In WLED, GPIO pins are used for the LED data signal, button inputs, relay control, and IR receivers. Not all GPIO pins are equal — some have restrictions on the ESP32 (e.g. GPIO 0, 2, 15 affect boot mode).

Green-Red-Blue. The colour data order used by most WS2812B LED ICs. Despite being marketed as RGB LEDs, the IC expects green data first, then red, then blue. WLED handles this automatically when the correct LED type is selected, but manually setting the wrong order will cause incorrect colours.

Free RAM available to WLED at runtime. Visible on the WLED Info page. Low heap (below 10KB) indicates memory pressure, which can cause instability, OTA failure, or crashes. Common causes: too many segments, too many LEDs, or complex usermod configurations. The ESP32 has significantly more heap than the ESP8266.

A hardware interface standard used by large LED matrix panels (the kind used in commercial LED displays and scoreboards). WLED 16 added native HUB75 support via the ESP32, enabling direct drive of these high-density panels. Requires specific ESP32 GPIO wiring for the parallel data interface.

Ingress Protection rating — a two-digit standard indicating resistance to solids and liquids. For LED strips: IP30 (bare, indoor only), IP65 (silicone coated, splash-resistant), IP67 (sealed tube, temporary submersion), IP68 (fully submersible). Higher IP ratings make soldering more difficult and reduce flexibility.

WLED’s primary control interface — a RESTful HTTP API that accepts and returns JSON data. Allows external systems (Home Assistant, Node-RED, custom software) to control every aspect of WLED programmatically. Full documentation at kno.wled.ge/interfaces/json-api.

A circuit that converts logic voltage levels between the 3.3V output of ESP32/ESP8266 microcontrollers and the 5V data input expected by most LED strips (WS2812B, SK6812, etc.). The SN74AHCT125 is the most recommended level shifter for WLED builds. Some ESP32 GPIO pins can reliably drive 5V logic directly, but a level shifter is always safer.

LED Control peripheral on the ESP32. WLED uses LEDC for PWM-based dimming of non-addressable (analog) LED strips. Not to be confused with addressable LED control, which uses RMT or I2S.

Multicast DNS. A protocol that allows WLED to be found on a local network by hostname (e.g. "wled.local") without knowing its IP address. Configured in Config → Wi-Fi Setup. Requires mDNS-compatible routers — some older or more restrictive routers block multicast traffic.

Message Queuing Telemetry Transport. A lightweight publish/subscribe messaging protocol commonly used in home automation. WLED supports MQTT for receiving commands and publishing state updates. Enables integration with Home Assistant (via MQTT broker), Node-RED, OpenHAB, and custom automation systems.

Adafruit’s brand name for their WS2812B-compatible addressable LEDs and strips. "NeoPixel" is often used colloquially to refer to any single-wire addressable LED, though technically it refers to Adafruit’s specific products. All NeoPixels are WS2812B-compatible and work perfectly with WLED.

Over-The-Air update. WLED supports wireless firmware updates via the web interface or ArduinoOTA protocol, so you can update to a new WLED version without physically connecting to the controller via USB. Requires adequate free heap memory and a stable Wi-Fi connection during the update.

A set of colours used by WLED effects to determine which colours to display. WLED includes 50+ built-in palettes (Ocean, Lava, Forest, Party, etc.) plus custom palette support. The palette selector is visible alongside effect selection in the WLED UI. Effects that support palettes are marked with a palette icon.

The practice of connecting additional power wires from the PSU directly to points along the LED strip (not just the beginning). Required for longer strips where voltage drop would otherwise cause dimming or colour shift toward the far end. Always connect both +V and GND at each injection point.

A saved state in WLED including effect, palette, brightness, colour, and segment configuration. Presets can be recalled instantly via the WLED UI, API, physical buttons, or schedules. WLED supports up to 250 presets, and presets can be chained into playlists.

Power Supply Unit. For LED installations, this is a dedicated DC power supply (typically 5V or 12V) capable of delivering sufficient current for your strip. Always use a PSU rated for at least 20% more current than your calculated peak draw. Do not use USB phone chargers for anything beyond ~30 LEDs.

A 300–500Ω resistor placed in series on the data wire between the controller and LED strip, as close to the controller output as possible. Prevents signal reflections that cause flickering. Mandatory for reliable operation. For data lines longer than 1.5m, use 470Ω.

Remote Control Transceiver — a hardware peripheral on the ESP32 used by WLED to generate the precise timing signals required by single-wire LED protocols (WS2812B, SK6812, etc.). The ESP32 has 8 RMT channels, allowing up to 8 simultaneous LED outputs without software timing.

A defined section of one or more LED outputs that can have its own independent effect, palette, colour, and brightness settings. Segments allow a single strip to display different effects on different sections simultaneously. Multiple segments on the same strip share the same data line but display independently.

An RGBW addressable LED chipset — like WS2812B but with a dedicated white LED element in addition to red, green, and blue. Uses the same single-wire protocol. Available in warm white, neutral white, and cool white variants. Produces significantly better whites than RGB colour mixing.

Serial Peripheral Interface. A two-wire synchronous protocol using separate data (MOSI) and clock (SCK) lines. Used by APA102, SK9822, and LPD8806 strips. The separate clock line eliminates timing constraints, enabling much higher data rates than single-wire protocols like WS2812B.

User Datagram Protocol synchronisation. A WLED feature that allows multiple WLED controllers to mirror each other’s state in real-time over a local network. One device acts as master, others as receivers. Configured in Config → Sync. Useful for large multi-strip installations where all strips should show the same effect.

A plugin system in WLED that allows community-contributed features to be added without modifying WLED’s core code. Popular usermods include temperature sensors, rotary encoders, battery level monitoring, IR remote control, and MPU6050 motion detection. Found in the WLED GitHub repository under the usermods folder.

The reduction in voltage that occurs along the length of a wire or LED strip due to electrical resistance. In LED strips, voltage drop causes LEDs near the end of the strip to appear dimmer or display incorrect colours. Mitigated by using thicker wire, shorter runs, and power injection. Calculated as V = I × R.

An addressable LED driver IC that controls groups of three LEDs (one RGB pixel per IC). Lower effective resolution than WS2812B (each "pixel" covers 3 LEDs). Commonly found in cheaper 12V strips. Well-supported in WLED. Because one IC drives 3 LEDs, effects appear chunkier — each "step" covers 3 physical LEDs.

The most popular addressable RGB LED chipset in the maker community. Each LED contains its own control IC. Uses a single data wire with precise timing (800kHz). Available in densities from 30 to 144 LEDs per metre. Operates at 5V. The default choice for most WLED builds due to widespread availability, low cost, and excellent community support.

A 12V individually addressable LED strip with a backup data line. Higher voltage than WS2812B means lower current for equivalent brightness, reducing voltage drop on longer runs. The backup data line prevents a single dead LED from breaking the chain. A good choice for permanent installations over 5 metres.