Custom Dictionary Mac How to Create and Manage It

You add a clinician's surname to your Mac, dictate it into a note, and watch it become a different word. A developer dictates an API name, gets an ordinary dictionary term, and misses the substitution until the code comment is already published. A product manager adds a client name in one app, only to find that another app still underlines or replaces it.

The problem usually isn't that your Mac has no custom dictionary. It's that macOS has several vocabulary layers, and they don't all influence the same kind of text input. The right fix depends on whether you're correcting spellcheck, helping Voice Control recognize a command, or improving a speech recognizer that creates text.

This guide separates LocalDictionary, Contacts, and Voice Control vocabulary, then shows when a system-level entry is enough and when an app-level dictionary, such as the one in AIDictation, is more appropriate. It also covers local storage, privacy, synchronization, and the testing routine that prevents silent substitutions.

If your workflow depends on Apple-platform customization beyond spelling, a personalization project for Apple provides useful context for how Mac experiences can be designed.

Table of Contents

• Why Your Mac Keeps Misspelling Names and Technical Terms
  • The three layers in practical terms
• Understanding Where macOS Stores Custom Words
  • LocalDictionary and spelling files
  • Contacts and Voice Control
• How to Create Import and Edit Your Custom Dictionary on Mac
  • Inspecting the local file
  • Checking Dictionary settings and lookup
• Using App Level Custom Dictionaries Including AIDictation
• Testing Syncing and Keeping Your Dictionary Accurate
  • Sync is a separate problem
• Keep Your Custom Dictionary Working for You

Why Your Mac Keeps Misspelling Names and Technical Terms

A dictated patient name such as “Mireles” can become a familiar word. A developer's “Kubernetes” may appear inconsistently, while “FHIR” arrives with the wrong capitalization. These errors can survive review because the substituted word is grammatically valid, so spellcheck has no reason to flag it.

macOS separates spelling, contacts, Voice Control, and dictation recognition. Adding a term to the spelling vocabulary can remove a red underline or prevent autocorrection, but it does not teach the speech recognizer how the term sounds. Adding a contact can improve recognition of a person or organization name, yet it is not a technical glossary. Voice Control has its own vocabulary feature, and Apple's Voice Control vocabulary guidance applies that feature to Voice Control rather than ordinary keyboard dictation. A command may work in Voice Control while the same spoken term fails in Notes or a browser.

The three layers in practical terms

• LocalDictionary: Add names, product terms, and jargon that macOS should accept as correctly spelled. This helps text already produced by typing or dictation, but does not guarantee the recognizer will output the preferred form.
• Contacts: Use this layer for people and organizations already represented in your address book. It can help with names without filling the general spelling vocabulary with contact-specific entries.
• Voice Control vocabulary: Add custom spoken commands or terms used within Voice Control workflows. These entries do not provide universal correction for every dictation engine.

The distinction matters in clinical notes and developer documentation. A spelling entry may keep “PostgreSQL” from being marked wrong after transcription, while the recognizer still produces a sound-alike. System vocabulary also has different privacy and synchronization implications from an app-level dictionary. For recognizer-level control, an app such as AIDictation must inject custom terms into transcription or provide an effective correction workflow. Choose that route when exact output matters more than a spelling check alone. A personalization project for Apple offers further context on Mac customization.

Understanding Where macOS Stores Custom Words

Mac's Dictionary app has been part of macOS since OS X 10.4 Tiger, released in 2005. The first version included the New Oxford American Dictionary and Oxford American Writer's Thesaurus, creating a system-level reference layer that later supported broader lookup and custom spelling workflows. Apple expanded the reference set in subsequent releases, adding Japanese dictionaries in OS X 10.5 Leopard, the British Oxford Dictionary of English in OS X 10.7 Lion, and French, German, Spanish, and Chinese dictionaries in OS X 10.8. (Dictionary's macOS history) documents that progression.

That history helps explain why the modern system can feel fragmented. The Dictionary app is primarily a reference tool, while the spelling service and speech features use their own vocabulary mechanisms.

LocalDictionary and spelling files

The practical spelling layer lives in the current user's Library. A published Mac guide identifies custom spelling files in ~/Library/Spelling/, including an en file and LocalDictionary that can be inspected or edited. These files are local to the Mac, which is useful when names or terminology shouldn't leave the device, but it also means you shouldn't assume the entries will appear automatically on another Mac.

This is the layer to use when apps rely on macOS spelling services. It's not a replacement for every app's own dictionary. Electron-based applications, editors, terminals, and transcription tools may store or interpret vocabulary independently.

Contacts and Voice Control

Contacts is best treated as a name source, not a technical dictionary. It can provide useful recognition context for people and organizations, but it won't manage a structured list of drug names, internal project codes, or API identifiers.

Voice Control is different again. Apple provides a dedicated vocabulary workflow for Voice Control, including custom words and phrases for spoken interaction. That vocabulary belongs to Voice Control's command-and-control system. It shouldn't be confused with a universal list for the keyboard dictation service.

For a separate explanation of converting recordings into text, see this guide to an audio-to-text converter for Mac workflows. The important decision is simple: choose the storage layer according to the failure you're fixing, not according to whichever dictionary setting you happen to find first.

How to Create Import and Edit Your Custom Dictionary on Mac

The safest way to begin is to add one troublesome term through the spelling menu, then test it before building a large vocabulary file. Open TextEdit or another app that uses macOS spelling services, type the word, select it, and Control-click it. Choose the option that teaches or learns the spelling, commonly shown as Learn Spelling.

This is appropriate for a surname, product name, medication name, or technical term that macOS keeps treating as an error. Preserve the spelling exactly as it should appear, including capitalization and accents. If “Navicat” is a product name or “eGFR” is a clinical abbreviation, enter the form you want to see in finished text.

Inspecting the local file

For direct review, open Finder, choose Go, hold Option, select Library, and open the Spelling folder. You can also use Finder's Go to Folder command and enter:

~/Library/Spelling/

Look for LocalDictionary and the language file relevant to your setup. Back up the folder before editing anything. A plain-text editor is preferable to a rich-text editor because formatting characters can corrupt a simple word list.

Add entries one per line unless the file already uses a different established format. Don't casually replace the entire file. Make a copy first, preserve a known-good version, and edit only the terms you understand.

Practical rule: Add a small batch, close the editor, and test before importing a large vocabulary list.

Bulk editing can help developers and technical writers who repeatedly use names such as GraphQL, PostgreSQL, or an internal service name. It can also help clinical teams maintain recurring terminology, but a spelling list alone won't guarantee correct dictation. It tells the spelling service that a token is acceptable. It doesn't necessarily tell a speech recognizer which pronunciation or competing sound should win.

Checking Dictionary settings and lookup

Apple provides a Dictionary settings flow where you can select or deselect reference sources. Open Dictionary, access its settings, and review the enabled dictionaries for the languages you use. This controls what Dictionary can consult during lookup, not necessarily which words a transcription engine will produce.

You can verify a term in supported apps with Control-click or a three-finger tap on the trackpad. These lookup gestures are useful for checking definitions and available sources, while the spelling menu is the relevant place for teaching the system a new accepted spelling. If you're new to Mac dictation itself, this practical guide on how to dictate on MacBook can help separate dictation controls from spelling controls.

After changing LocalDictionary, relaunch affected apps. Some applications won't reload the vocabulary until they restart, and a full Mac restart may be necessary. Test the exact word, its capitalization, and a similar-sounding alternative rather than assuming that a successful Learn Spelling action solved recognition.

For a focused walkthrough of the local vocabulary workflow, see how to add a word to the Mac dictionary.

Using App Level Custom Dictionaries Including AIDictation

A system spelling dictionary works after text has been entered or recognized. An app-level custom dictionary operates closer to transcription, helping the recognizer interpret a sound as a name, acronym, or technical term. Adding “Xamarin” to LocalDictionary may prevent a spelling warning, yet dictation can still produce a different word.

macOS has three vocabulary layers with separate jobs. LocalDictionary supports spelling services and autocorrection across compatible apps. Contacts can help the system recognize names already stored in your address book, but it is a poor place for a large technical glossary. Voice Control has its own custom vocabulary for commands and recognition. Its entries do not become a universal vocabulary for standard keyboard dictation or every application.

AIDictation provides an app-level option for Mac users who need names and technical terms handled during voice-to-text. Its product description includes a custom dictionary and context rules that can change formatting by app. Auto Mode, Local Mode using Parakeet v3 on Apple Silicon, and Cloud Mode with AI cleanup and context-aware formatting each make different privacy and connectivity trade-offs. Choose a local mode when audio must stay on the Mac. Cloud processing may suit workflows that accept sending audio or text to a service.

Use LocalDictionary for recurring written terms, Contacts for recognizable personal names, and Voice Control vocabulary for voice commands or terms recognized through Voice Control. Use an app dictionary when the error occurs during transcription and matters inside a specific dictation workflow.

For clinicians, a local mode alone does not establish suitability for protected health information. Confirm your organization's privacy and compliance requirements before dictating patient data.

This custom dictionary setup guide covers app vocabulary configuration and dictation testing.

Testing Syncing and Keeping Your Dictionary Accurate

Adding a term is only half the job. A custom dictionary can create a false sense of security if the exact word works in one app but a near-conflicting word appears in another. Silent substitution is more dangerous than an obvious misspelling because the sentence may look normal during a quick review.

Use a compact verification routine immediately after adding important vocabulary:

• Exact word: Dictate the term in a natural sentence and confirm every letter.
• Near-conflict: Test a homophone or similar-sounding word that could appear in the same context.
• Capitalization: Check the preferred form for names, acronyms, product names, and code identifiers.
• Cross-app behavior: Test in the apps where the term matters, such as an EHR editor, Xcode, a browser form, or a messaging client.

If you added the term through LocalDictionary, relaunch the affected application. Some apps need a complete restart, and macOS may need to restart before the new vocabulary is recognized consistently. Don't judge success from the app where you made the change. Test the destination app that produces the costly error.

Sync is a separate problem

LocalDictionary entries are stored locally in the user Library. That's a privacy advantage, especially for sensitive internal names or clinical terminology, but it also means you shouldn't treat the file as a cloud-synced profile. If you work across Macs, maintain a controlled backup of ~/Library/Spelling/ and transfer entries deliberately, while respecting workplace policies.

Voice Control vocabulary has its own management boundary and should be reviewed separately. It may help with spoken commands, but it won't automatically solve every standard dictation failure. Contacts-based names also have different behavior from manually learned spellings, so adding a person to Contacts isn't a substitute for testing the actual dictation path.

Research on contextual vocabulary injection supports this layered approach. One study reported transcription accuracy moving from 75% to 88% when an untrained system became minimally trained, and from 91% to 94% after a customized dictionary and pronunciations were added to a moderately trained system. Another contextual-biasing study using Whisper reported word error rate changes from 40.27% to 29.26% on its tiny model and from 27.82% to 11.12% on its medium model, while entity detection rose from 67% to 98%. (The cited study document also highlights the limitation: improvements concentrate on domain terms, names, and alphanumeric sequences rather than all speech.

Keep sensitive vocabulary on-device when possible, back up before major system changes, and remove obsolete entries. A smaller, tested dictionary is more useful than a large list nobody verifies.

Keep Your Custom Dictionary Working for You

A reliable custom dictionary Mac workflow starts with diagnosis. Use LocalDictionary for spelling acceptance, Contacts for names, and Voice Control vocabulary for Voice Control commands. Use an app-level dictionary when the failure happens during speech recognition rather than after text appears.

Build gradually from real errors. Add the highest-impact terms first, test their exact spelling and likely sound-alikes, then expand only when your work exposes another recurring failure. Review the list periodically, remove stale project names, and keep a backup of ~/Library/Spelling/ before system maintenance.

Privacy should guide the final choice. Local storage keeps entries on the Mac, while cloud-assisted dictation may provide richer cleanup or context handling but requires a separate review of data handling. For clinical, engineering, and multilingual workflows, accuracy matters most when the vocabulary reflects the words you use, not an oversized dictionary copied from somewhere else.

---

AIDictation provides Mac dictation with custom vocabulary for names and technical terms, plus local and cloud modes for different privacy and formatting needs. If you want to test a dictation layer that connects vocabulary management with cleaned-up writing, visit AIDictation and choose the mode that fits your workflow.