# How to Create and Apply Custom Styles in Word Documents Using OfficeCLI > Learn to create and apply custom styles in Word documents with OfficeCLI. Effortlessly manage styles using path-based commands for efficient document customization. - Repository: [OfficeAI/OfficeCLI](https://github.com/iofficeai/OfficeCLI) - Tags: how-to-guide - Published: 2026-08-09 --- **OfficeCLI treats Word document styles as first-class objects in the OOXML `/styles` part, enabling you to create, modify, and apply custom styles using path-based commands with O(1) cached lookup performance.** The iOfficeAI/OfficeCLI repository provides a command-line interface for manipulating Office Open XML documents programmatically. When working with Word documents, understanding how to create and apply custom styles is essential for maintaining consistent formatting across large document automation workflows. ## Understanding the OfficeCLI Style Architecture OfficeCLI implements Word document styling as a semantic model mapped directly to the OOXML package structure. All styles reside in the `/styles` part of the document package and are accessible through the same path-based commands used for other document elements. The `WordHandler` class maintains a `_styleByIdCache` dictionary for O(1) style lookup performance. When you first query a style, the `FindStyleById` method populates this cache by walking the `` collection【/cache/repos/github.com/iOfficeAI/OfficeCLI/main/src/officecli/Handlers/WordHandler.cs#L56-L71】. Any mutation to the styles part triggers `InvalidateStyleIndex` to ensure the cache remains synchronized with the live document model. For performance-critical operations, OfficeCLI employs a fast-path mutation strategy. The `RawSet` method detects `/styles` targets and uses a compiled XPath matcher `/^/w:styles/w:style\[@w:styleId='([^']*)'\]$/` to replace individual `` nodes without reparsing the entire part【/cache/repos/github.com/iOfficeAI/OfficeCLI/main/src/officecli/Handlers/WordHandler.cs#L1894-L1916】. ## Creating Custom Styles To define a new style, use the `add` command targeting `/styles` with `--type style` and specify properties that map directly to the `` element attributes. ### Defining a Paragraph Style The following example creates a custom paragraph style named "MyHeading" based on the built-in Heading1 style: ```bash officecli add report.docx /styles --type style \ --prop styleId=MyHeading \ --prop type=paragraph \ --prop name="My Heading" \ --prop basedOn=Heading1 \ --prop font=Georgia \ --prop size=16pt \ --prop color=#2A7AE2 ``` Key properties include: - **styleId**: Unique identifier for the style (required) - **type**: Style type (`paragraph`, `character`, `table`, or `numbering`) - **basedOn**: Parent style ID to inherit formatting from - **name**: Display name shown in Word's style gallery - **font**, **size**, **color**: Formatting attributes The [`src/officecli/CommandBuilder.Add.cs`](https://github.com/iOfficeAI/OfficeCLI/blob/main/src/officecli/CommandBuilder.Add.cs) file parses these `--prop` arguments and routes them to the OpenXML style builder before persisting to the document. ## Applying Styles to Document Elements Once created, apply styles by setting the `style` property on any document element. The style reference uses the `styleId` value defined during creation. ```bash officecli add report.docx /body --type paragraph \ --prop text="Executive Summary" \ --prop style=MyHeading ``` This command creates a new paragraph in the document body and applies the custom "MyHeading" style. The style assignment modifies the paragraph's `w:pPr/w:pStyle` element in the underlying OOXML. ## Modifying and Removing Styles OfficeCLI supports both surgical updates to existing styles and complete removal. ### Updating Existing Styles Use the `set` command with an XPath targeting the specific style node to modify properties without recreating the entire style definition: ```bash officecli set report.docx /styles/Style[@w:styleId='MyHeading'] \ --prop color=#D9534F ``` This operation leverages the `RawSet` fast-path to update only the color property while preserving all other formatting attributes. ### Deleting Styles Remove style definitions entirely using the `remove` command: ```bash officecli remove report.docx /styles/Style[@w:styleId='MyHeading'] ``` ## Querying Available Styles Inspect all styles present in a document using the `view` command: ```bash officecli view report.docx /styles ``` This outputs the complete styles gallery, including both built-in Word styles and custom definitions you've added. ## Summary - OfficeCLI stores Word styles in the `/styles` OOXML part accessible through path-based commands - The `WordHandler` maintains a `_styleByIdCache` for O(1) style lookups and uses `InvalidateStyleIndex` to keep the cache current - Create styles with `add /styles --type style` and properties like `styleId`, `basedOn`, `font`, and `color` - Apply styles to elements using the `style` property in `add` or `set` commands - Update styles efficiently via `RawSet` compiled XPath matching without full part reparsing - Reference implementation details in [`src/officecli/Handlers/WordHandler.cs`](https://github.com/iOfficeAI/OfficeCLI/blob/main/src/officecli/Handlers/WordHandler.cs) lines 56-71 and 1894-1916 ## Frequently Asked Questions ### What file format does OfficeCLI use for Word documents? OfficeCLI operates on the Office Open XML (OOXML) format used by modern Word documents (.docx). The tool manipulates the underlying XML parts directly, including the `/styles` part that contains all style definitions as `` elements. ### How does OfficeCLI handle style lookup performance? The `WordHandler` class implements a caching strategy using `_styleByIdCache` to achieve O(1) lookups after the initial style discovery. The `FindStyleById` method populates this cache on first access by iterating through the `` collection. When styles are modified, `InvalidateStyleIndex` clears the cache to ensure subsequent operations read the updated definitions. ### Can I base custom styles on built-in Word styles? Yes. Use the `basedOn` property when creating a style to inherit formatting from any existing style, including built-in Word styles like Heading1, Normal, or Title. This creates a style hierarchy where your custom style inherits default formatting that you can override with specific properties like `font` or `color`. ### Is it possible to apply styles to elements other than paragraphs? Absolutely. The `type` property when creating styles supports `paragraph`, `character`, `table`, and `numbering` values. When applying styles, you can reference character styles for runs of text, table styles for table elements, or paragraph styles for block-level elements depending on the target element's capabilities.