diff --git a/package.json b/package.json
index 9de3e95..8ce1b63 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
     "query-string": "^6.2.0",
     "react": "latest",
     "react-dom": "latest",
+    "react-intl": "^2.8.0",
     "react-router-dom": "^4.3.1",
     "semantic-ui-css": "^2.4.1",
     "semantic-ui-react": "^0.84.0",
@@ -22,6 +23,7 @@
     "@types/query-string": "^6.2.0",
     "@types/react": "*",
     "@types/react-dom": "*",
+    "@types/react-intl": "^2.3.15",
     "@types/react-router-dom": "^4.3.1",
     "@types/jest": "*",
     "@types/node": "*",
@@ -35,7 +37,7 @@
     "start": "react-scripts-ts start",
     "build": "react-scripts-ts build",
     "test": "react-scripts-ts test --env=jsdom",
-    "prettier": "prettier --write src/**/*.{ts,tsx}",
+    "prettier": "prettier --write src/**/*.{ts,tsx,json}",
     "predeploy": "npm run build",
     "deploy": "gh-pages -d build"
   },
diff --git a/src/index.tsx b/src/index.tsx
index 5f4939f..51ad9c2 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -1,21 +1,35 @@
+import * as locale_en from 'react-intl/locale-data/en';
+import * as locale_pl from 'react-intl/locale-data/pl';
+import * as messages_pl from './translations/pl.json';
 import * as React from 'react';
 import * as ReactDOM from 'react-dom';
+import {addLocaleData} from 'react-intl';
 import {ChartView} from './chart_view';
 import {HashRouter as Router, Route, Switch} from 'react-router-dom';
+import {IntlProvider} from 'react-intl';
 import {Intro} from './intro';
 import {TopBar} from './top_bar';
-import 'semantic-ui-css/semantic.min.css';
 import './index.css';
+import 'semantic-ui-css/semantic.min.css';
+
+addLocaleData([...locale_en, ...locale_pl]);
+
+const messages = {
+  pl: messages_pl,
+};
+const language = navigator.language && navigator.language.split(/[-_]/)[0];
 
 ReactDOM.render(
-  <Router>
-    <div className="root">
-      <Route component={TopBar} />
-      <Switch>
-        <Route exact path="/" component={Intro} />
-        <Route exact path="/view" component={ChartView} />
-      </Switch>
-    </div>
-  </Router>,
+  <IntlProvider locale={language} messages={messages[language]}>
+    <Router>
+      <div className="root">
+        <Route component={TopBar} />
+        <Switch>
+          <Route exact path="/" component={Intro} />
+          <Route exact path="/view" component={ChartView} />
+        </Switch>
+      </div>
+    </Router>
+  </IntlProvider>,
   document.querySelector('#root'),
 );
diff --git a/src/intro.tsx b/src/intro.tsx
index c574a0d..c022519 100644
--- a/src/intro.tsx
+++ b/src/intro.tsx
@@ -1,6 +1,7 @@
 import * as queryString from 'query-string';
 import * as React from 'react';
 import {Card} from 'semantic-ui-react';
+import {FormattedMessage} from 'react-intl';
 import {Link} from 'react-router-dom';
 
 /** Link that loads a GEDCOM file from URL. */
@@ -18,25 +19,49 @@ function GedcomLink(props: {url: string; text: string}) {
 export function Intro() {
   return (
     <Card className="intro">
-      <Card.Content header="Topola Genealogy Viewer" />
+      <Card.Content>
+        <Card.Header>
+          <FormattedMessage
+            id="intro.title"
+            defaultMessage="Topola Genealogy Viewer"
+          />
+        </Card.Header>
+      </Card.Content>
       <Card.Content>
         <p>
-          Topola Genealogy is a genealogy tree viewer that lets you browse the
-          structure of the family.
+          <FormattedMessage
+            id="intro.description"
+            defaultMessage={
+              'Topola Genealogy is a genealogy tree viewer that lets you' +
+              ' browse the structure of the family.'
+            }
+          />
         </p>
         <p>
-          Use the LOAD FROM URL or LOAD FROM FILE buttons above to load a GEDCOM
-          file. You can export a GEDCOM file from most of the existing genealogy
-          programs and web sites.
+          <FormattedMessage
+            id="intro.instructions"
+            defaultMessage={
+              'Use the LOAD FROM URL or LOAD FROM FILE buttons above to load' +
+              ' a GEDCOM file. You can export a GEDCOM file from most of the' +
+              ' existing genealogy programs and web sites.'
+            }
+          />
+        </p>
+        <p>
+          <FormattedMessage
+            id="intro.examples"
+            defaultMessage={
+              'Here are some examples from the web that you can view:'
+            }
+          />
         </p>
-        <p>Here are some examples from the web that you can view:</p>
         <ul>
           <li>
             <GedcomLink
               url="http://genpol.com/module-Downloads-prep_hand_out-lid-32.html"
               text="Karol Wojtyła"
             />{' '}
-            (from{' '}
+            (<FormattedMessage id="intro.from" defaultMessage="from" />{' '}
             <a href="http://genpol.com/module-Downloads-display-lid-32.html">
               GENPOL
             </a>
@@ -47,7 +72,7 @@ export function Intro() {
               url="https://webtreeprint.com/tp_downloader.php?path=famous_gedcoms/shakespeare.ged"
               text="Shakespeare"
             />{' '}
-            (from{' '}
+            (<FormattedMessage id="intro.from" defaultMessage="from" />{' '}
             <a href="https://webtreeprint.com/tp_famous_gedcoms.php">
               webtreeprint.com
             </a>
@@ -58,7 +83,7 @@ export function Intro() {
               url="http://genealogyoflife.com/tng/gedcom/HarryPotter.ged"
               text="Harry Potter"
             />{' '}
-            (from{' '}
+            (<FormattedMessage id="intro.from" defaultMessage="from" />{' '}
             <a href="http://famousfamilytrees.blogspot.com/">
               Famous Family Trees
             </a>
diff --git a/src/top_bar.tsx b/src/top_bar.tsx
index 73a23b8..cfbed40 100644
--- a/src/top_bar.tsx
+++ b/src/top_bar.tsx
@@ -1,6 +1,7 @@
 import * as md5 from 'md5';
 import * as queryString from 'query-string';
 import * as React from 'react';
+import {FormattedMessage} from 'react-intl';
 import {Link} from 'react-router-dom';
 import {RouteComponentProps} from 'react-router-dom';
 import {
@@ -86,7 +87,14 @@ export class TopBar extends React.Component<RouteComponentProps, State> {
         onClose={() => this.handleClose()}
         centered={false}
       >
-        <Header icon="cloud download" content="Load from URL" />
+        <Header>
+          <Icon name="cloud download" />
+          <FormattedMessage
+            id="load_from_url.title"
+            defaultMessage="Load from URL"
+            children={(txt) => txt}
+          />
+        </Header>
         <Modal.Content>
           <Form onSubmit={() => this.handleLoad()}>
             <Input
@@ -95,22 +103,33 @@ export class TopBar extends React.Component<RouteComponentProps, State> {
               onChange={(e) => this.handleUrlChange(e)}
               ref={(ref) => (this.inputRef = ref!)}
             />
-            <p className="comment">
-              Data from the URL will be loaded through{' '}
-              <a href="https://cors-anywhere.herokuapp.com/">
-                cors-anywhere.herokuapp.com
-              </a>{' '}
-              to avoid CORS issues.
+            <p>
+              <FormattedMessage
+                id="load_from_url.comment"
+                defaultMessage={
+                  'Data from the URL will be loaded through {link} to avoid CORS issues.'
+                }
+                values={{
+                  link: (
+                    <a href="https://cors-anywhere.herokuapp.com/">
+                      cors-anywhere.herokuapp.com
+                    </a>
+                  ),
+                }}
+              />
             </p>
           </Form>
         </Modal.Content>
         <Modal.Actions>
-          <Button
-            secondary
-            content="Cancel"
-            onClick={() => this.handleClose()}
-          />
-          <Button primary content="Load" onClick={() => this.handleLoad()} />
+          <Button secondary onClick={() => this.handleClose()}>
+            <FormattedMessage
+              id="load_from_url.cancel"
+              defaultMessage="Cancel"
+            />
+          </Button>
+          <Button primary onClick={() => this.handleLoad()}>
+            <FormattedMessage id="load_from_url.load" defaultMessage="Load" />
+          </Button>
         </Modal.Actions>
       </Modal>
     );
@@ -124,7 +143,10 @@ export class TopBar extends React.Component<RouteComponentProps, State> {
         </Link>
         <Menu.Item as="a" onClick={() => this.handleLoadFromUrl()}>
           <Icon name="cloud download" />
-          Load from URL
+          <FormattedMessage
+            id="menu.load_from_url"
+            defaultMessage="Load from URL"
+          />
         </Menu.Item>
         <input
           className="hidden"
@@ -135,7 +157,10 @@ export class TopBar extends React.Component<RouteComponentProps, State> {
         <label htmlFor="fileInput">
           <Menu.Item as="a">
             <Icon name="folder open" />
-            Load from file
+            <FormattedMessage
+              id="menu.load_from_file"
+              defaultMessage="Load from file"
+            />
           </Menu.Item>
         </label>
         <Menu.Item
diff --git a/src/translations/pl.json b/src/translations/pl.json
new file mode 100644
index 0000000..4f554f4
--- /dev/null
+++ b/src/translations/pl.json
@@ -0,0 +1,13 @@
+{
+  "menu.load_from_url": "Otwórz URL",
+  "menu.load_from_file": "Otwórz plik",
+  "intro.title": "Topola Genealogy",
+  "intro.description": "Topola Genealogy pozwala przeglądać drzewo genealogiczne w interaktywny sposób.",
+  "intro.instructions": "Kliknij OTWÓRZ URL lub OTWÓRZ PLIK, aby załadować plik GEDCOM. Większość programów genealogicznych posiada funkcję eksportu do pliku GEDCOM.",
+  "intro.examples": "Poniżej jest kilka przykładów znalezionych w Internecie:",
+  "intro.from": "źródło:",
+  "load_from_url.title": "Otwórz z adresu URL",
+  "load_from_url.comment": "Dane z podanego adresu URL zostaną załadowane poprzez usługę {link} w celu uniknięcia problemów z CORS.",
+  "load_from_url.cancel": "Anuluj",
+  "load_from_url.load": "Otwórz"
+}
diff --git a/tsconfig.json b/tsconfig.json
index cbc11ab..3e852eb 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -17,7 +17,8 @@
     "noImplicitAny": true,
     "strictNullChecks": true,
     "suppressImplicitAnyIndexErrors": true,
-    "noUnusedLocals": true
+    "noUnusedLocals": true,
+    "resolveJsonModule": true
   },
   "exclude": [
     "node_modules",
diff --git a/tslint.json b/tslint.json
index afcf72d..132ab0b 100644
--- a/tslint.json
+++ b/tslint.json
@@ -55,5 +55,8 @@
       "allow-trailing-underscore",
       "allow-pascal-case"
     ]
+  },
+  "linterOptions": {
+    "exclude": "src/**/*.json"
   }
 }