# XLSX Template Filler Fill existing styled/formula Excel templates by replacing {{variable}} placeholders only > Canonical page: https://elysiatools.com/en/tools/xlsx-template-filler - **Category:** Format Conversion - **Keywords:** xlsx, template, placeholder, exceljs, report ## Overview Fill placeholders without breaking template design. - Preserves workbook styles, formulas, and merged cells - Replaces only text placeholders like `{{customer.name}}` - Supports strict mode for missing variables ## Inputs - **Template Excel File** (file) - **Variables JSON** (textarea): { "customer": { "name": "Alice" }, "invoice_no": "INV-2026-001" } - **Strict Mode** (checkbox) ## When to use - Generating recurring invoices or reports based on a fixed visual design. - Populating Excel templates with dynamic data from external JSON sources. - Maintaining consistent branding and styling across bulk-generated spreadsheets. ## How it works - Upload your existing Excel file containing {{variable}} placeholders. - Provide a JSON object mapping your data to those specific placeholders. - Process the file to generate a new spreadsheet with the data injected while keeping all original styles intact. ## Use cases - Automating the creation of monthly financial statements from database exports. - Generating personalized client project status reports using a standardized template. - Batch-producing inventory manifests or shipping labels from a central data source. ## Frequently asked questions ### Will this tool break my existing formulas? No, the tool specifically targets text placeholders and leaves your formulas and cell references untouched. ### Does it support nested JSON data? Yes, you can use dot notation in your placeholders, such as {{customer.name}}, to access nested values in your JSON. ### What happens if a placeholder is missing in the JSON? If Strict Mode is disabled, the placeholder remains as-is. If enabled, the tool will flag the missing variable. ### Can I use this for files with merged cells? Yes, the tool is designed to preserve the layout, including merged cells and custom styling. ### Are there limits on the template file size? The tool supports files up to 200MB, ensuring you can handle large, data-heavy report templates. ## Related tools - [XLSX Formula Injector](https://elysiatools.com/en/tools/xlsx-formula-injector): Fill formulas down worksheet columns and optionally lock formula cells for protected, template-friendly Excel workbooks - [XLSX Column Mapper](https://elysiatools.com/en/tools/xlsx-column-mapper): Rename, reorder, and drop Excel columns with alias matching and case/whitespace normalization - [XLSX Named Range Injector](https://elysiatools.com/en/tools/xlsx-named-range-injector): Create or update workbook-level named ranges so formulas, validations, and reusable templates can reference stable Excel names - [XLSX Chart Embedder](https://elysiatools.com/en/tools/xlsx-chart-embedder): Embed generated chart images into Excel workbooks using workbook data ranges for bar or pie chart reports - [XLSX Conditional Formatting Rule](https://elysiatools.com/en/tools/xlsx-conditional-formatting-rule): Batch-apply conditional formatting rules such as threshold highlights, data bars, and color scales to Excel worksheets - [XLSX Data Validation Dropdown](https://elysiatools.com/en/tools/xlsx-data-validation-dropdown): Batch-create dropdowns, dependent cascading dropdowns, and input prompts in Excel workbooks using data validation rules - [XLSX Print Setup Pack](https://elysiatools.com/en/tools/xlsx-print-setup-pack): Apply paper, margins, scaling, repeating titles, and header/footer print settings to Excel workbooks in one pass - [XLSX Sparkline Injector](https://elysiatools.com/en/tools/xlsx-sparkline-injector): Inject Excel sparklines into worksheet cells by patching XLSX sheet XML with sparkline definitions ## Samples - [XLSX Samples](https://elysiatools.com/en/samples/xlsx-samples): Sample XLSX spreadsheets for worksheet parsing and data extraction testing - [XLS Samples](https://elysiatools.com/en/samples/xls-samples): Sample legacy Excel (XLS) files for binary spreadsheet parsing and import tests - [Android Serialization Java Samples](https://elysiatools.com/en/samples/android-serialization-java): Android Java serialization examples including JSON serialization, deserialization, and XML parsing - [Android Serialization Kotlin Samples](https://elysiatools.com/en/samples/android-serialization-kotlin): Android Kotlin serialization examples including JSON serialization, deserialization, and XML parsing ## Related content - [Templated Document Generation Workflow](https://elysiatools.com/en/hubs/templated-document-generation): Create repeatable forms, certificates, report cards, invoices, receipts, storyboards, DOCX merges, PDF documents, and XLSX template outputs from structured inputs. - [KPI Report Pack Workflows](https://elysiatools.com/en/hubs/kpi-report-pack-workflows): Turn API and spreadsheet data into KPI dashboards, multi-tab Excel report packs, branded sheets, charts, sparklines, and executive PDF or Markdown reports.