Build Custom Tools

Overview

Custom tools are drag-and-drop content blocks you create for the Unlayer editor. Each tool needs:

• A renderer (what users see in the editor)
• Exporters (HTML output — must be table-based for email)
• Property editors (the settings panel)

Complete Example: Product Card

This is a fully working custom tool with an image, title, price, and buy button:

unlayer.registerTool({
  name: 'product_card',
  label: 'Product Card',
  icon: 'fa-shopping-cart',
  supportedDisplayModes: ['web', 'email'],

  options: {
    content: {
      title: 'Content',
      position: 1,
      options: {
        productTitle: {
          label: 'Product Title',
          defaultValue: 'Product Name',
          widget: 'text',               // → values.productTitle = 'Product Name'
        },
        productImage: {
          label: 'Image',
          defaultValue: { url: 'https://via.placeholder.com/300x200' },
          widget: 'image',              // → values.productImage.url = 'https://...'
        },
        price: {
          label: 'Price',
          defaultValue: '$99.99',
          widget: 'text',               // → values.price = '$99.99'
        },
        buttonText: {
          label: 'Button Text',
          defaultValue: 'Buy Now',
          widget: 'text',
        },
        buttonLink: {
          label: 'Button Link',
          defaultValue: { name: 'web', values: { href: 'https://example.com', target: '_blank' } },
          widget: 'link',               // → values.buttonLink.values.href = 'https://...'
        },
      },
    },
    colors: {
      title: 'Colors',
      position: 2,
      options: {
        titleColor: {
          label: 'Title Color',
          defaultValue: '#333333',
          widget: 'color_picker',       // → values.titleColor = '#333333'
        },
        buttonBg: {
          label: 'Button Background',
          defaultValue: '#007bff',
          widget: 'color_picker',
        },
      },
    },
  },

  values: {},

  renderer: {
    Viewer: unlayer.createViewer({
      render(values) {
        return `
          <div style="text-align: center; padding: 20px;">
            <img src="${values.productImage.url}" style="max-width: 100%;" />
            <h3 style="color: ${values.titleColor};">${values.productTitle}</h3>
            <p style="font-size: 24px; font-weight: bold;">${values.price}</p>
            <a href="${values.buttonLink.values.href}"
               style="display: inline-block; background: ${values.buttonBg};
                      color: #fff; padding: 12px 24px; text-decoration: none;
                      border-radius: 4px;">
              ${values.buttonText}
            </a>
          </div>
        `;
      },
    }),

    exporters: {
      web(values) {
        return `
          <div style="text-align: center; padding: 20px;">
            <img src="${values.productImage.url}" alt="${values.productTitle}" style="max-width: 100%;" />
            <h3 style="color: ${values.titleColor};">${values.productTitle}</h3>
            <p style="font-size: 24px; font-weight: bold;">${values.price}</p>
            <a href="${values.buttonLink.values.href}" target="${values.buttonLink.values.target}"
               style="display: inline-block; background: ${values.buttonBg};
                      color: #fff; padding: 12px 24px; text-decoration: none;">
              ${values.buttonText}
            </a>
          </div>
        `;
      },
      email(values) {
        // Email MUST use tables — divs break in Outlook/Gmail
        return `
          <table width="100%" cellpadding="0" cellspacing="0" border="0">
            <tr><td align="center" style="padding: 20px;">
              <img src="${values.productImage.url}" alt="${values.productTitle}"
                   style="max-width: 100%; display: block;" />
            </td></tr>
            <tr><td align="center" style="padding: 10px;">
              <h3 style="color: ${values.titleColor}; margin: 0;">${values.productTitle}</h3>
            </td></tr>
            <tr><td align="center">
              <p style="font-size: 24px; font-weight: bold; margin: 5px 0;">${values.price}</p>
            </td></tr>
            <tr><td align="center" style="padding: 15px;">
              <table cellpadding="0" cellspacing="0" border="0">
                <tr><td style="background: ${values.buttonBg}; border-radius: 4px;">
                  <a href="${values.buttonLink.values.href}" target="${values.buttonLink.values.target}"
                     style="display: inline-block; color: #fff; padding: 12px 24px;
                            text-decoration: none;">
                    ${values.buttonText}
                  </a>
                </td></tr>
              </table>
            </td></tr>
          </table>
        `;
      },
    },

    head: {
      css(values) {
        return `#${values._meta.htmlID} img { max-width: 100%; height: auto; }`;
      },
      js(values) { return ''; },
    },
  },

  validator(data) {
    const { values, defaultErrors } = data;
    const errors = [];
    if (!values.productTitle) {
      errors.push({
        id: 'PRODUCT_TITLE_REQUIRED',
        icon: 'fa-warning',
        severity: 'ERROR',
        title: 'Missing product title',
        description: 'Product title is required',
      });
    }
    if (!values.productImage?.url) {
      errors.push({
        id: 'PRODUCT_IMAGE_REQUIRED',
        icon: 'fa-warning',
        severity: 'ERROR',
        title: 'Missing product image',
        description: 'Product image is required',
      });
    }
    return [...errors, ...defaultErrors];
  },
});

Register it at init time with the custom# prefix:

unlayer.init({
  tools: {
    'custom#product_card': {          // REQUIRED: custom# prefix
      data: {
        apiEndpoint: '/api/products', // Custom data accessible in renderer
      },
      properties: {
        // Override default property values or dropdown options
      },
    },
  },
});

---

Widget Value Access Reference

How to read each widget type's value in your renderer:

Widget	Default Value	Access in render(values)
text	'Hello'	values.myField → 'Hello'
rich_text	'<p>Hello</p>'	values.myField → '<p>Hello</p>'
html	'<div>...</div>'	values.myField → '<div>...</div>'
color_picker	'#FF0000'	values.myField → '#FF0000'
alignment	'center'	values.myField → 'center'
font_family	{label:'Arial', value:'arial'}	values.myField.value → 'arial'
image	{url: 'https://...'}	values.myField.url → 'https://...'
toggle	false	values.myField → false
link	{name:'web', values:{href,target}}	values.myField.values.href → 'https://...'
counter	'10'	values.myField → '10' (string!)
dropdown	'option1'	values.myField → 'option1'
datetime	'2025-01-01'	values.myField → '2025-01-01'
border	{borderTopWidth:'1px',...}	values.myField.borderTopWidth → '1px'

Dropdown options — pass via unlayer.init() under the tool's properties config:

unlayer.init({
  tools: {
    'custom#product_card': {
      properties: {
        department: {
          editor: {
            data: {
              options: [
                { label: 'Sales', value: 'sales' },
                { label: 'Support', value: 'support' },
              ],
            },
          },
        },
      },
    },
  },
});

---

Custom Property Editor (React)

For controls beyond built-in widgets:

const RangeSlider = ({ label, value, updateValue, data }) => (
  <div>
    <label>{label}: {value}px</label>
    <input
      type="range"
      min={data.min || 0}
      max={data.max || 100}
      value={parseInt(value)}
      onChange={(e) => updateValue(e.target.value + 'px')}
    />
  </div>
);

unlayer.registerPropertyEditor({
  name: 'range_slider',
  Widget: RangeSlider,
});

// Use in your tool:
borderRadius: {
  label: 'Corner Radius',
  defaultValue: '4px',
  widget: 'range_slider',
  data: { min: 0, max: 50 },
},

---

Validator Return Format

Each error must include id, icon, severity, title, and description:

validator(data) {
  const { values, defaultErrors } = data;
  const errors = [];

  if (!values.productTitle) {
    errors.push({
      id: 'PRODUCT_TITLE_REQUIRED',     // Unique error ID
      icon: 'fa-warning',                // FontAwesome icon
      severity: 'ERROR',                 // 'ERROR' | 'WARNING'
      title: 'Missing product title',    // Short label
      description: 'Product title is required',  // Detailed message
    });
  }

  if (values.price && !values.price.startsWith('$')) {
    errors.push({
      id: 'PRICE_MISSING_CURRENCY',
      icon: 'fa-dollar-sign',
      severity: 'WARNING',
      title: 'Missing currency symbol',
      description: 'Price should include currency symbol',
      labelPath: 'price',               // Optional — highlights the property in the panel
    });
  }

  return [...errors, ...defaultErrors];  // Merge with built-in errors
}

---

Email-Safe HTML Patterns

Email clients (Outlook, Gmail) require table-based HTML. Copy-paste these patterns:

Button:

<table cellpadding="0" cellspacing="0" border="0">
  <tr><td style="background: #007bff; border-radius: 4px;">
    <a href="URL" style="display: inline-block; color: #fff; padding: 12px 24px; text-decoration: none;">
      Button Text
    </a>
  </td></tr>
</table>

Two columns:

<table width="100%" cellpadding="0" cellspacing="0">
  <tr>
    <td width="50%" valign="top" style="padding: 10px;">Left</td>
    <td width="50%" valign="top" style="padding: 10px;">Right</td>
  </tr>
</table>

Safe CSS properties: color, background-color, font-size, font-family, font-weight, text-align, padding, margin, border, width, max-width, display: block/inline-block.

Unsafe (avoid in email): flexbox, grid, position, float, box-shadow, border-radius (partial support), calc().

---

Common Mistakes

Mistake	Fix
Missing custom# prefix	Tools MUST use custom#my_tool in tools config at init
Div-based email exporter	Email exporters MUST return table-based HTML
Forgetting _meta.htmlID	Scope CSS: #${values._meta.htmlID} { ... }
Hardcoded values in renderer	Use values object — let property editors drive content
Wrong dropdown options format	Pass options via unlayer.init() under tools['custom#name'].properties.prop.editor.data.options

Troubleshooting

Problem	Fix
Tool doesn't appear in editor	Check supportedDisplayModes includes current mode
Properties panel is empty	Check options structure — needs group → options nesting
Custom editor doesn't update	Ensure updateValue() is called with the new value
Exported HTML looks different	Check both Viewer.render() and exporters.email/web()

Resources

• Create Custom Tool
• Property Editors
• Advanced Options
• Built-in Tools