> ## Documentation Index > Fetch the complete documentation index at: https://docs.sendx.io/llms.txt > Use this file to discover all available pages before exploring further. # Personalization & Merge Tags > Use merge tags to insert dynamic values — names, custom fields, links, and images — into email templates and transactional emails. SendX lets you insert dynamic, per-recipient values into your email content using **merge tags**. Use them to greet a contact by name, drop in an order amount, render a dynamic image, or build a personalized button link. ## Syntax SendX renders email content with **Go's template engine**, so every merge tag is wrapped in double curly braces and **must start with a leading dot (`.`)**: ``` {{.VariableName}} ``` **The leading dot is required.** `{{.FirstName}}` works; `{{FirstName}}` (no dot) does **not** — it will fail to render and your template will appear to "not take effect." This is the single most common personalization mistake. | You want to insert… | Use this | Renders as | | ------------------------- | ----------------------------------------------- | --------------------------------------------------- | | A text value | `Hi {{.FirstName}}!` | `Hi Jane!` | | A value inside a sentence | `Your order {{.orderId}} is confirmed.` | `Your order A12345 is confirmed.` | | A dynamic image | `` | `` | | A dynamic button/link | `{{.buttonLabel}}` | `Pay now` | Merge tags work anywhere in the template — in the subject line, in body text, and inside HTML attributes like `src` and `href`. ## Personalizing transactional emails (`POST /send/template`) When you send a transactional email with a saved template, you supply the per-recipient values in the **`customFields`** object on each `to` entry. Every key you pass becomes a merge tag of the same name. Keys map **verbatim**: the key `orderId` populates `{{.orderId}}`, `amount` populates `{{.amount}}`, and so on. You do **not** need to pre-define these as custom fields in your account — any ad-hoc key works for transactional sends. **Template HTML (saved in SendX):** ```html theme={null}

{{.accountName}} update

Hi {{.firstName}}, we received your payment of {{.amount}}.

receipt {{.buttonLabel}} ``` **Request:** ```bash theme={null} curl -X POST "https://api.sendx.io/api/v1/rest/send/template" \ -H "Content-Type: application/json" \ -H "X-Team-ApiKey: YOUR_API_KEY" \ -d '{ "from": { "email": "support@example.com", "name": "Acme" }, "to": [ { "email": "jane@acme.com", "name": "Jane", "customFields": { "accountName": "Acme", "firstName": "Jane", "amount": "$42.00", "imageUrl": "https://cdn.example.com/receipt.png", "buttonUrl": "https://app.example.com/pay/A12345", "buttonLabel": "View receipt" } } ], "subject": "{{.accountName}} update", "template": "template_qmK2dMPNoQDobfxI4yMM7k" }' ``` **Rendered email:** ```html theme={null}

Acme update

Hi Jane, we received your payment of $42.00.

receipt View receipt ``` ### Variables available in transactional templates The transactional send path builds a minimal data context. The following are available in a `/send/template` render: | Merge tag | Source | | --------------- | ---------------------------------- | | `{{.Name}}` | The recipient's `name` field | | `{{.Email}}` | The recipient's `email` field | | `{{.}}` | Any key you pass in `customFields` | In transactional templates, `{{.FirstName}}`, `{{.LastName}}`, and `{{.Company}}` exist but default to **empty** unless you pass them yourself in `customFields`. The richer native tags below (e.g. `{{.ViewInBrowserLink}}`, `{{.GlobalUnsubscribeLink}}`) are **only** populated for campaign, drip, and workflow sends — not transactional sends. For transactional unsubscribe handling, use the `List-Unsubscribe` header. ## Personalizing campaigns & automations For campaigns, drip sequences, and workflow emails, SendX pulls values from the contact's stored profile, so a richer set of native tags is available automatically: | Merge tag | Description | | ---------------------------- | --------------------------------------------------------- | | `{{.FirstName}}` | Contact's first name | | `{{.LastName}}` | Contact's last name | | `{{.Name}}` | First + last name | | `{{.Email}}` | Contact's email address | | `{{.Company}}` | Contact's company | | `{{.CreatedDate}}` | Date the contact was added (`YYYY-MM-DD`) | | `{{.ViewInBrowserLink}}` | "View in browser" URL | | `{{.GlobalUnsubscribeLink}}` | Unsubscribe URL | | `{{.Address}}` | Your account's physical mailing address (CAN-SPAM footer) | Custom fields are referenced by their **name**, e.g. a custom field named `City` becomes `{{.City}}`. See [Custom field naming rules](#custom-field-naming-rules) below. ## Default (fallback) values If a value might be missing or blank, wrap it with the `fallback` helper so the email never shows an empty gap: ``` Hi {{fallback .FirstName "there"}}! ``` If `FirstName` is empty, this renders `Hi there!`. The SendX editor inserts this form automatically for every merge tag, using `"there"` as the default — so review the defaults if you want something other than "there" to appear for blank values. ## Conditional content & loops Because SendX uses Go templates, you can conditionally show content or loop over lists. **Conditional:** ```html theme={null} {{if .couponCode}}

Use code {{.couponCode}} for 10% off!

{{else}}

Thanks for being a customer.

{{end}} ``` **Loop** (the values must be passed as a list): ```html theme={null} ``` ## Helper functions A few useful helpers are available inside tags (used as `{{helper arg1 arg2}}`): | Helper | Example | Description | | ---------------------------------------------- | ------------------------------------ | ----------------------------------------------- | | `fallback` | `{{fallback .FirstName "there"}}` | Returns the default if the value is empty/blank | | `capitalize_words` | `{{capitalize_words .city}}` | Title-cases the value | | `first_character` | `{{first_character .FirstName}}` | First character (e.g. for an avatar initial) | | `formatdate` | `{{formatdate .date "02 Jan 2006"}}` | Formats a date | | `todaydate` / `tomorrowdate` / `yesterdaydate` | `{{todaydate "02 Jan 2006"}}` | Relative date helpers | | `days_until` / `days_since` | `{{days_until .expiry}}` | Day-count helpers | ## Custom field naming rules When you create a custom field in SendX, the **name** you pick becomes its merge tag. A few rules apply: * Names are sanitized to letters, digits, and underscores — any other character (including spaces) becomes `_`. A field named `Order ID` becomes the tag `{{.Order_ID}}`. * These names are **reserved** (they collide with native attributes) and can't be used for custom fields: `email`, `firstname`, `lastname`, `company`, `name`. * For transactional `customFields` keys, use the same rule of thumb — stick to letters, digits, and underscores, and don't start a key with a digit, so it can be addressed as `{{.key}}`. The opaque IDs you see in the REST API (e.g. `custom_field_MnuqBAG2NPLm7PZMWbjQxt`) are **not** what you use in templates. Templates always reference custom fields by their human-readable **name**. ## Troubleshooting The most common cause is a **missing leading dot**. Use `{{.FirstName}}`, not `{{FirstName}}`. Also confirm: * The variable name matches exactly (it's case-sensitive — `{{.firstName}}` ≠ `{{.FirstName}}`). * For transactional sends, the key exists in the recipient's `customFields` object. * You're editing and sending the correct template ID. The field had no value for that recipient. Pass the value in `customFields` (transactional) or set it on the contact (campaigns). Empty values wrapped in `{{fallback .X "there"}}` render the default — change the default text if "there" isn't what you want. Those campaign-level system variables aren't injected for transactional `/send/template` sends. Only `{{.Name}}`, `{{.Email}}`, and your `customFields` keys are available there.