Macros

Lingui Macro provides powerful macros to transform JavaScript objects and JSX elements into ICU MessageFormat messages at compile time. It provides a more efficient and developer-friendly way to handle internationalization in your project.

The benefits of using macros:

You don't have to learn ICU MessageFormat syntax. You always use familiar JS and JSX code.
Components and functions are type checked.
Short IDs are generated for your messages.
Additional validation of plural rules is performed during transformation.
Non-essential data is removed from the production build (e.g. comments and default messages) to save a few bytes.

There are two types of macros: Core Macros (JS) and React Macros (JSX).

Core Macros

Core (JS) Macros can be used in any JavaScript context (e.g. outside JSX). All JS macros are transformed into a Message Descriptor wrapped inside of i18n._ call:

import { t } from "@lingui/core/macro";
t`Attachment ${name} saved`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
i18n._(
  /*i18n*/ {
    id: "nwR43V",
    message: "Attachment {name} saved",
    values: { name },
  }
);

/*i18n*/ comment

In the example above you may notice the /*i18n*/ comment in the macro output. This comment tells the extract plugin that the following object should be collected into the message catalog.

Message Descriptor is an object with a message ID, default message and other parameters:

type MessageDescriptor = {
  id: string;
  message?: string;
  values?: Record<string, any>;
  comment?: string;
};

The id is the message ID and is the only parameter required. The id and message are extracted into the message catalog. Only id and values are used at runtime, all other attributes are removed from the production code for size optimization.

You don't need to specify the ID manually. By default, Macro will automatically create a short ID from your message. However, you can explicitly specify a custom ID. Read more about Explicit vs Generated IDs.

`t`

The most common macro for messages. It transforms tagged template literal into message in ICU MessageFormat:

import { t } from "@lingui/core/macro";
const message = t`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "mY42CM",
    message: "Hello World",
  }
);

Message variables are supported:

import { t } from "@lingui/core/macro";
const message = t`My name is ${name}`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "mVmaLu",
    message: "My name is {name}",
    values: { name },
  }
);

In fact, any expression can be used inside template literal. However, only simple variables are referenced by name in a transformed message. All other expressions are referenced by their numeric index:

import { t } from "@lingui/core/macro";
const message = t`Today is ${new Date()}`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = i18n._(
  /*i18n*/ {
    id: "2aJT27",
    message: "Today is {0}",
    values: { 0: new Date() },
  }
);

Optionally, a custom i18n instance can be passed that can be used instead of the global instance:

import { t } from "@lingui/core/macro";
import { i18nCustom } from "./lingui";
const message = t(i18nCustom)`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18nCustom } from "./lingui";
const message = i18nCustom._(
  /*i18n*/ {
    id: "mY42CM",
    message: "Hello World",
  }
);

info

By default the i18n object is imported from @lingui/core. If you are using a custom instance of the i18n object, you need to set runtimeConfigModule or pass a custom instance to t.

It's also possible to pass custom id and comment for translators by calling t macro with a message descriptor:

import { t } from "@lingui/core/macro";
const message = t({
  id: "msg.hello",
  comment: "Greetings at the homepage",
  message: `Hello ${name}`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "msg.hello",
    comment: "Greetings at the homepage",
    message: "Hello {name}",
    values: { name },
  }
);

In this case, message is used as the default message, and it's transformed as if it were wrapped in a t macro. message also accepts any other macros:

import { t } from "@lingui/core/macro";
const message = t({
  id: "msg.plural",
  message: plural(value, { one: "...", other: "..." }),
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "msg.plural",
    message: "{value, plural, one {...} other {...}}",
    values: { value },
  }
);

`plural`

Pluralization is a common problem in i18n. Different languages have different rules for plural form (e.g. English has only one and other, while Czech has one, few, many and other). The plural macro is used to handle this.

plural(value: string | number, options: Object)

The value specifies the plural form or cardinal number. The second argument, options, is an object with available plural forms:

import { plural } from "@lingui/core/macro";
const message = plural(count, {
  one: "# Book",
  other: "# Books",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "V/M0Vc",
    message: "{count, plural, one {# Book} other {# Books}}",
    values: { count },
  }
);

tip

Choose the plural forms used in your source code based on the pluralization rules of your source locale.

If you need to add variables in plural form, you can use template string literals. This time you don't need the t macro, because template strings are transformed automatically:

import { plural } from "@lingui/core/macro";
const message = plural(count, {
  one: `${name} has # friend`,
  other: `${name} has # friends`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "CvuUwE",
    message: "{count, plural, one {{name} has # friend} other {{name} has # friends}}",
    values: { count, name },
  }
);

Plurals can also be nested to form complex messages. Here's an example using two counters:

import { plural } from "@lingui/core/macro";
const message = plural(numBooks, {
  one: plural(numArticles, {
    one: `1 book and 1 article`,
    other: `1 book and ${numArticles} articles`,
  }),
  other: plural(numArticles, {
    one: `${numBooks} books and 1 article`,
    other: `${numBooks} books and ${numArticles} articles`,
  }),
});

// ↓ ↓ ↓ ↓ ↓ ↓
// Generated message was wrapped for better readability

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "XnUh4j",
    message: `{numBooks, plural,
         one {{numArticles, plural,
            one {1 book and 1 article}
            other {1 book and {numArticles} articles}
         }}
         other {{numArticles, plural,
            one {{numBooks} books and 1 article}
            other {{numBooks} books and {numArticles} articles}
         }}
      }`,
    values: { numBooks, numArticles },
  }
);

This is just one example of how macros can be combined to create a complex message. However, simple is better, because in the end it's the translator who has to translate these long and complex strings.

tip

Use plural inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: plural(count, {
    one: "# Book",
    other: "# Books",
  }),
});

`selectOrdinal`

SelectOrdinal is a variation of the plural macro. It's used to handle ordinal numbers (e.g. 1st, 2nd, 3rd, 4th, etc.).

selectOrdinal(value: string | number, options: Object)

The value specifies the ordinal number. The second argument, options, is an object with available ordinal forms:

import { selectOrdinal } from "@lingui/core/macro";
const message = selectOrdinal(count, {
  one: "#st",
  two: "#nd",
  few: "#rd",
  other: "#th",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";
const message = i18n._(
  /*i18n*/ {
    id: "V8xI3w",
    message: "{count, selectOrdinal, one {#st} two {#nd} few {#rd} other {#th}}",
    values: { count },
  }
);

tip

Use selectOrdinal inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: selectOrdinal(count, {
    one: "#st",
    two: "#nd",
    few: "#rd",
    other: "#th",
  }),
});

`select`

The select macro is used to handle different forms of a message based on a value.

select(value: string | number, options: Object)

It works like a switch statement - it selects one of the forms provided in the options object based on the value:

import { select } from "@lingui/core/macro";
const message = select(gender, {
  male: "he",
  female: "she",
  other: "they",
});

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = i18n._(
  /*i18n*/ {
    id: "VRptzI",
    message: "{gender, select, male {he} female {she} other {they}}",
    values: { gender },
  }
);

tip

Use select inside t or defineMessage macro if you want to add custom id, context or comment for translators.

const message = t({
  id: "my.custom.id",
  comment: "My Comment",
  message: select(gender, {
    male: "he",
    female: "she",
    other: "they",
  }),
});

`defineMessage` / `msg`

The defineMessage (alias: msg) macro allows to define a message for later use. It has the same signature as t and returns a MessageDescriptor that you can pass to i18n._ to get a translated string at any time later. This is useful for lazy translations.

In other words, t returns a translated string at the time when it's called, while msg returns a MessageDescriptor that can produce translated strings later:

import { i18n } from "@lingui/core";
import { defineMessage } from "@lingui/core/macro";

// define message
const message = defineMessage`Hello World`;

// use it later
i18n._(message);

// ↓ ↓ ↓ ↓ ↓ ↓

import { i18n } from "@lingui/core";

const message = /*i18n*/ {
  id: "mY42CM",
  message: "Hello World",
};

// use it later
i18n._(message);

You can also use a shorter alias of the defineMessage macro:

import { msg } from "@lingui/core/macro";
const message = msg`Hello World`;

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "mY42CM",
  message: "Hello World",
};

The defineMessage macro also supports a MacroMessageDescriptor object as input. This can be used to provide additional information for the message such as comment or context:

type MacroMessageDescriptor = {
  id?: string;
  message?: string;
  comment?: string;
  context?: string;
};

Either the id or message property is required. id is a custom message ID. If it isn't set, the message (and context if present) will be used to generate an ID. Read more about Explicit vs Generated IDs.

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  id: "Navigation / About",
  message: "About us",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "Navigation / About",
  message: "About us",
};

The message is a default message. Any JS macro can be used here. Template string literals don't need to be tagged with t.

import { defineMessage } from "@lingui/core/macro";
const name = "Joe";
const message = defineMessage({
  message: `Welcome, ${name}!`,
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "dgJjNB",
  message: "Welcome, {name}",
  values: {
    name,
  },
};

The comment is a comment for translators. It's extracted into the message catalog, and it gives translators additional information about the message. It's removed from the production code:

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  comment: "Link in navigation pointing to About page",
  message: "About us",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "+mNwru",
  comment: "Link in navigation pointing to About page",
  message: "About us",
};

Note

In the production build, the macro is stripped of message, comment and context properties:

import { defineMessage } from "@lingui/core/macro";
const message = defineMessage({
  id: "msg.navigation.about",
  comment: "Link in navigation pointing to About page",
  message: "About us",
  context: "Context about the link",
});

// process.env.NODE_ENV === "production"
// ↓ ↓ ↓ ↓ ↓ ↓

const message = /*i18n*/ {
  id: "msg.navigation.about",
};

message and comment are used in message catalogs only. context is used only for generating ID and is stripped from the output.

React Macros

React (JSX) Macros are used in JSX elements and are transformed into the Trans component imported from the @lingui/react package.

`Trans`

The Trans macro is used to translate static messages, messages with variables and messages with inline markup:

import { Trans } from "@lingui/react/macro";
<Trans>Refresh inbox</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id="EsCV2T" message="Refresh inbox" />;

Available Props:

Prop Name	Type	Description
`id`	string	Custom message ID
`comment`	string	Comment for translators
`context`	string	Allows to extract the same messages with different IDs
`render`	func	Custom render callback to render translation

`id`

Each message in the catalog is identified by a message ID. While macro uses message (and context property if provided) to generate the ID, it's possible to provide custom ID. Read more about Explicit vs Generated IDs.

import { Trans } from "@lingui/react/macro";
<Trans id="message.attachment_saved">Attachment {name} saved.</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id="message.attachment_saved" message="Attachment {name} saved." />;

`comment`

Comment for translators to give them additional information about the message. It will be visible in the TMS if it is supported, and in the catalog format. It will be removed from production code.

`context`

Allows to extract the same messages with different IDs. It is useful when the same message has different meanings in different contexts. See Context for more details.

Similarly to comment, it will be added to the message catalog, visible in TMS and will be removed from the production code:

import { Trans } from "@lingui/react/macro";
<Trans context="direction">right</Trans>;
<Trans context="correctness">right</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"d1wX4r"} message="right" />;
<Trans id={"16eaSK"} message="right" />;

This macro is particularly useful if the message contains inline markup:

import { Trans } from "@lingui/react/macro";

<Trans>
  Read the <a href="/docs">docs</a>.
</Trans>;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"mk8bSG"} message="Read the <0>docs</0>." components={{ 0: <a href="/docs" /> }} />;

Components and HTML tags are replaced by dummy indexed tags (<0></0>) which has several advantages:

Both custom React components and built-in HTML tags are supported.
Changing component props doesn't break translation.
The message is extracted as a whole sentence (this seems to be obvious, but most i18n libs simply split the message into pieces by tags and translate them separately).

`render`

Custom render callback to render translation. This prop is passed directly to the Trans component from the @lingui/react package.

`Plural`

The Plural JSX macro is used to handle plural forms. It's similar to the plural core macro, but is used in JSX elements.

import { Plural } from "@lingui/react/macro";
<Plural value={numBooks} one="Book" other="Books" />;

// ↓ ↓ ↓ ↓ ↓ ↓

import { Trans } from "@lingui/react";
<Trans id={"is7n96"} message="{numBooks, plural, one {Book} other {Books}}" values={{ numBooks }} />;

Available Props:

Prop name	Type	Description
`other`	string	(required) general plural form
`value`	number	(required) Value is mapped to plural form below
`format`	string\|Object	Number format passed as options to `Intl.NumberFormat`
`offset`	number	Offset of value when calculating plural forms
`zero`	string	Form for empty `value`
`one`	string	Singular form
`two`	string	Dual form
`few`	string	Paucal form
`many`	string	Plural form
`_<number>`	string	Exact match form, corresponds to `=N` rule
`id`	string	Custom message ID
`comment`	string	Comment for translators
`context`	string	Allows to extract the same messages with different IDs
`render`	func	Custom render callback to render translation

Exact matches in MessageFormat syntax are expressed as =int (e.g. =0), but in React this isn't a valid prop name. Therefore, exact matches are expressed as _int prop (e.g. _0). This is commonly used in combination with offset prop. offset affects only plural forms, not exact matches.

import { Plural } from "@lingui/react/macro";

<Plural
  value={count}
  offset={1}
  // when value == 0
  _0="Nobody arrived"
  // when value == 1
  _1="Only you arrived"
  // when value == 2
  // value - offset = 1 -> `one` plural form
  one="You and # other guest arrived"
  // when value >= 3
  other="You and # other guests arrived"
/>;

/*
  This is transformed to Trans component with ID:
  {count, plural, offset:1 _0    {Nobody arrived}
                           _1    {Only you arrived}
                           one   {You and # other guest arrived}
                           other {You and # other guests arrived}}
*/

`SelectOrdinal`

The SelectOrdinal JSX macro is used to handle ordinal numbers. It's similar to the selectOrdinal core macro, but is used in JSX elements.

import { SelectOrdinal } from "@lingui/react/macro";

// count == 1 -> 1st
// count == 2 -> 2nd
// count == 3 -> 3rd
// count == 4 -> 4th
<SelectOrdinal value={count} one="#st" two="#nd" few="#rd" other="#th" />;

Available Props:

Prop name	Type	Description
`value`	number	(required) Value is mapped to plural form below
`other`	string	(required) general plural form
`offset`	number	Offset of value for plural forms
`zero`	string	Form for empty `value`
`one`	string	Singular form
`two`	string	Dual form
`few`	string	Paucal form
`many`	string	Plural form
`_<number>`	string	Exact match form, correspond to `=N` rule. (e.g: `_0`, `_1`)
`format`	string\|Object	Number format passed as options to `Intl.NumberFormat`

`Select`

The Select JSX macro is used to handle different forms of a message based on a value. It's similar to the select core macro, but is used in JSX elements.

import { Select } from "@lingui/react/macro";

// gender == "female"      -> Her book
// gender == "male"        -> His book
// gender == "non-binary"  -> Their book
<Select value={gender} _male="His book" _female="Her book" other="Their book" />;

Available Props:

Prop name	Type	Description
`value`	number	(required) Value determines which form is output
`other`	number	(required) Default, catch-all form
`_<case>`	string	Form for specific case
`id`	string	Custom message ID
`comment`	string	Comment for translators
`context`	string	Allows to extract the same messages with different IDs
`render`	func	Custom render callback to render translation

The select cases except other should be prefixed with underscore: _male or _female.

`useLingui`

The useLingui React macro gives access to a t macro that is bound to the local i18n object passed from the React context.

It returns an object with the following content:

Key	Type	Description
`i18n`	`I18n`	The `I18n` object instance passed to `I18nProvider`
`t`	`t`	Reference to the `t` macro described above
`defaultComponent`	`React.ComponentType`	the same `defaultComponent` passed to `I18nProvider`, if provided

Example usage:

import { useLingui } from "@lingui/react/macro";

function MyComponent() {
  const { t } = useLingui();
  const a = t`Text`;
}

// ↓ ↓ ↓ ↓ ↓ ↓

import { useLingui } from "@lingui/react";

function MyComponent() {
  const { _ } = useLingui();
  const a = _(
    /*i18n*/
    {
      id: "xeiujy",
      message: "Text",
    }
  );
}

caution

The useLingui React macro is available from Lingui v5.

More Examples

Examples of JS macros

t`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "EsCV2T",
    message: "Refresh inbox",
  }
);

t(customI18n)`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "EsCV2T",
    message: "Refresh inbox",
  }
);

t(customI18n)`Attachment ${name} saved`;

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "nwR43V",
    message: "Attachment {name} saved",
    values: { name },
  }
);

plural(count, {
  one: "# Message",
  other: "# Messages",
});

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "4w2nim",
    message: "{count, plural, one {# Message} other {# Messages}}",
    values: { count },
  }
);

t({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

i18n._(
  /*i18n*/ {
    id: "msg.refresh",
    message: "Refresh inbox",
  }
);

t(customI18n)({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

customI18n._(
  /*i18n*/ {
    id: "msg.refresh",
    message: "Refresh inbox",
  }
);

const msg = defineMessage`Refresh inbox`;

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "EsCV2T",
  message: "Refresh inbox",
};

const msg = defineMessage({
  id: "msg.refresh",
  message: "Refresh inbox",
});

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "msg.refresh",
  message: "Refresh inbox",
};

const msg = defineMessage({
  id: "msg.plural",
  message: plural(count, {
    one: "# Message",
    other: "# Messages",
  }),
});

// ↓ ↓ ↓ ↓ ↓ ↓

const msg = /*i18n*/ {
  id: "msg.plural",
  message: "{count, plural, one {# Message} other {# Messages}}",
  values: { count },
};

Examples of JSX macros

<Trans>Attachment {name} saved</Trans>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id={"nwR43V"}
   message="Attachment {name} saved"
   values={{ name }}
/>

<Plural
   value={count}
   one="# Message"
   other="# Messages"
/>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id={"4w2nim"}
   message="{count, plural, one {# Message} other {# Messages}}"
   values={{ count }}
/>

<Trans id="msg.refresh">
   Refresh inbox
</Trans>

// ↓ ↓ ↓ ↓ ↓ ↓

<Trans
   id="msg.refresh"
   message="Refresh inbox"
/>

Core Macros​

t​

plural​

selectOrdinal​

select​

defineMessage / msg​

React Macros​

Trans​

id​

comment​

context​

render​

Plural​

SelectOrdinal​

Select​

useLingui​

More Examples​

Examples of JS macros​

Examples of JSX macros​

Core Macros

`t`

`plural`

`selectOrdinal`

`select`

`defineMessage` / `msg`

React Macros

`Trans`

`id`

`comment`

`context`

`render`

`Plural`

`SelectOrdinal`

`Select`

`useLingui`

More Examples

Examples of JS macros

Examples of JSX macros