Glossary
Windows Speech API (SAPI)
The Windows Speech API (SAPI) is Microsoft's interface that lets Windows apps use speech recognition and text-to-speech without building the speech engine themselves. Windows.Media.SpeechRecognition is a separate API for command and control in Windows Runtime apps.
Updated October 16, 20264 cited facts, each traced to its source
Also called SAPI, Windows.Media.SpeechRecognition.
The Windows Speech API (SAPI) is Microsoft's programming interface for speech recognition and text-to-speech on Windows. Microsoft says it "dramatically reduces the code overhead" an application needs to use both 1. An app calls SAPI to listen for speech or to speak text, and it does not have to build that machinery itself.
SAPI is a developer interface, not a feature you open. You do not start it from a keyboard shortcut. The dictation you use every day on Windows comes from features such as voice typing and Voice Access, which have their own commands.
SAPI gives apps a shared recognizer
Within SAPI, an app works with a recognizer. Microsoft recommends a particular kind for most apps: "A shared recognizer that could possibly be shared with other speech recognition applications is recommended for most speech applications" 2. The recognizer can be shared with other speech applications, which is the option Microsoft prefers for most apps.
Example: a note-taking app adds a dictate button. It asks SAPI for a recognizer, receives the recognized words as text, and inserts them into the note.
Windows.Media.SpeechRecognition is a separate API
The second name in the aka list, Windows.Media.SpeechRecognition, belongs to a different surface. Microsoft describes it as enabling "speech recognition for command and control within Windows Runtime app" 3. Choose it when you are building a Windows Runtime app that needs commands, such as "open settings", rather than free dictation. The SAPI overview sits in Microsoft's previous-versions documentation, so check the current namespace before you start a new project.
A newer on-device API arrived in 2026
In June 2026 heise reported that Microsoft's new Windows speech recognition API "processes speech directly on the device" and does not need an internet connection 4. This is a news report of a developer interface, so read Microsoft's current documentation before you build on it.
Why it matters for dictation and typing
For a person typing or dictating, SAPI is the layer underneath, and you rarely see it. For a developer, the choice of interface shapes what the app can do: whether recognition runs on the device or in the cloud, which languages are available, and whether the app gets commands or free text. Those choices affect how private and how offline a dictation feature can be. The guide to offline speech to text on Windows explains which Windows dictation works without a connection, and the Windows dictation privacy guide covers when audio goes online.
Related terms and guides
Related terms: Windows Speech Recognition (WSR), Voice Access (Windows), Number and grid overlays (Voice Access), Online speech recognition and Azure AI Speech.
Read Windows Speech Recognition: deprecation and replacement for the older feature that Voice Access replaces. For the wider picture, see our overview of dictation on Windows.
Evidence
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Related terms
- Dictation on Windows: Voice Typing, Voice Access, AppsThe topic this term belongs to
- Azure AI SpeechAzure AI Speech is Microsoft's cloud speech service. Microsoft now calls it Azure Speech in Foundry Tools, and its speech to text powers the online recognition behind Windows voice typing, which needs an internet connection.
- Copilot+ PCA Copilot+ PC is a class of Windows 11 hardware with a neural processing unit (NPU) that Microsoft says can run at 40 or more trillion operations per second. Some newer Windows AI features, including fluid dictation, require this hardware.
- Fluid dictationFluid dictation is a Windows feature on Copilot+ PCs that corrects grammar, punctuation and filler words as you speak. Microsoft says it is powered by small language models that run on the device, and that you can undo a correction by saying Revert or Undo that.
- Neural processing unit (NPU)A neural processing unit (NPU) is a specialized chip for AI-intensive processes, such as real-time translation and image generation. Microsoft says many new Windows AI features require an NPU that can run at 40 or more trillion operations per second, and a speech model can run faster on one.
- Number and grid overlays (Voice Access)Number and grid overlays are Voice Access views for clicking things you cannot name. Show numbers puts a number on each clickable item so you can say it, and Show grid divides the screen into numbered tiles that narrow the mouse pointer step by step.
- Online speech recognitionOnline speech recognition sends your voice to a cloud service that turns it into text, instead of processing it on your PC. Microsoft says voice typing on Windows uses online speech recognition, which Microsoft describes as giving more accurate recognition.
- Phi SilicaPhi Silica is Microsoft's on-device language model, which runs on the neural processing unit of Copilot+ PCs. Microsoft says it is being replaced by Aion Instruct, and its voice typing help names it as the download to watch while fluid dictation gets ready.
- Speech pack (Windows)A speech pack is the set of on-device language files that Windows needs before it can recognize speech in a language offline. Microsoft says you must download a speech pack for a language in Voice access before you can use it, and the first download needs an internet connection.
- Voice Access (Windows)Voice Access is the Windows 11 feature that lets you control the whole PC and write text by voice, not only dictate. Microsoft says it works without an internet connection after setup, and it replaces Windows Speech Recognition.
- Voice typing launcherThe voice typing launcher is the Windows voice typing setting that lets you start dictation quickly when the cursor is in a text box. Microsoft lists it among the settings you open from the gear icon in the voice typing flyout.
- Windows key + H (Win+H)Windows key + H, written Win+H, is the keyboard shortcut that starts voice typing in Windows, so you can dictate into the text box where your cursor is. Microsoft says it does not start voice typing while Voice Access is running.
- Windows on ArmWindows on Arm is Windows running on processors that use the Arm instruction set instead of x86 or x64 chips. It runs native Arm apps and many unmodified x86 and x64 apps, and Microsoft says Arm-native apps give the best performance and battery life.