diff --git a/.gitignore b/.gitignore
index 5205805..a3d67c8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,3 +20,6 @@
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
+
+.idea
+package-lock.json
diff --git a/README.md b/README.md
index 54d0743..a59e6d6 100644
--- a/README.md
+++ b/README.md
@@ -12,5 +12,25 @@ clone github-contributions-chart & github-contributions-canvas
 - browse to http://localhost:3000/
 - select `JankariTech` theme
 - enter GitHub username
+- optionally enter the GitLab URL, username and access token (see below)
 - click `Generate`
 - download image
+
+## Include contributions from a private GitLab instance
+
+The chart can additionally contain the contributions a person made on a private GitLab instance.
+
+All GitLab settings are entered directly in the form, no configuration file is needed:
+
+- `GitLab URL` - the base URL of the GitLab instance, e.g. `https://gitlab.example.com`
+- `GitLab Username` - the username on that instance
+- `GitLab Access Token` - a personal access token with the `read_user` scope,
+  only needed if the instance / the profile is not publicly readable
+
+The contributions are read from `<GitLab URL>/users/<username>/calendar.json` by the server
+(the token is sent to the local API route in a header and only used for that request)
+and are added to the GitHub contributions of the same day.
+The daily counts and the yearly totals are summed up and the colour levels are recalculated.
+
+Note: only days that are part of the GitHub contribution calendar of the user are shown,
+so GitLab contributions of years in which the person had no GitHub activity at all are not displayed.
diff --git a/src/pages/api/v1/[username].js b/src/pages/api/v1/[username].js
index 8487fcd..16d9710 100644
--- a/src/pages/api/v1/[username].js
+++ b/src/pages/api/v1/[username].js
@@ -1,8 +1,20 @@
 import { fetchDataForAllYears } from '../../../utils/api/fetch'
 
 export default async (req, res) => {
-  const { username, format } = req.query;
-  const data = await fetchDataForAllYears(username, format);
-  res.setHeader('Cache-Control', 's-maxage=3600, stale-while-revalidate')
-  res.json(data);
-}
\ No newline at end of file
+  const { username, format, gitlabUsername, gitlabUrl } = req.query;
+  // the token is sent in a header so that it does not end up in URLs / logs
+  const gitlabToken = req.headers['x-gitlab-token'];
+  try {
+    const data = await fetchDataForAllYears(
+      username,
+      format,
+      gitlabUsername,
+      gitlabUrl,
+      gitlabToken
+    );
+    res.setHeader('Cache-Control', 's-maxage=3600, stale-while-revalidate')
+    res.json(data);
+  } catch (error) {
+    res.status(500).json({ error: error.message });
+  }
+}
diff --git a/src/pages/index.js b/src/pages/index.js
index 82da52a..29b783a 100644
--- a/src/pages/index.js
+++ b/src/pages/index.js
@@ -5,6 +5,8 @@ import {
   fetchData,
   downloadJSON,
   cleanUsername,
+  cleanGitlabUsername,
+  cleanGitlabUrl,
   share,
   copyToClipboard
 } from "../utils/export";
@@ -16,6 +18,9 @@ const App = () => {
   const contentRef = useRef();
   const [loading, setLoading] = useState(false);
   const [username, setUsername] = useState("");
+  const [gitlabUsername, setGitlabUsername] = useState("");
+  const [gitlabUrl, setGitlabUrl] = useState("");
+  const [gitlabToken, setGitlabToken] = useState("");
   const [theme, setTheme] = useState("standard");
   const [data, setData] = useState(null);
   const [error, setError] = useState(null);
@@ -31,15 +36,23 @@ const App = () => {
     e.preventDefault();
 
     setUsername(cleanUsername(username));
+    setGitlabUsername(cleanGitlabUsername(gitlabUsername));
+    setGitlabUrl(cleanGitlabUrl(gitlabUrl));
     setLoading(true);
     setError(null);
     setData(null);
 
-    fetchData(cleanUsername(username))
+    fetchData(cleanUsername(username), {
+      username: cleanGitlabUsername(gitlabUsername),
+      url: cleanGitlabUrl(gitlabUrl),
+      token: gitlabToken.trim()
+    })
       .then((data) => {
         setLoading(false);
 
-        if (data.years.length === 0) {
+        if (data.error) {
+          setError(data.error);
+        } else if (data.years.length === 0) {
           setError("Could not find your profile");
         } else {
           setData(data);
@@ -87,8 +100,8 @@ const App = () => {
       username: username,
       themeName: theme,
       scaleFactor: 12,
-      startingDate: '2020-12-08',
-      endDate: '2024-01-14',
+      startingDate: '2023-04-14',
+      endDate: '2026-07-31',
       footerText: "Made by @sallar & friends - github-contributions.vercel.app"
     });
     contentRef.current.scrollIntoView({
@@ -182,6 +195,32 @@ const App = () => {
           autoCapitalize="none"
           autoFocus
         />
+        <input
+          placeholder="GitLab URL (optional), e.g. https://gitlab.example.com"
+          onChange={(e) => setGitlabUrl(e.target.value)}
+          value={gitlabUrl}
+          id="gitlab-url"
+          autoCorrect="off"
+          autoCapitalize="none"
+        />
+        <input
+          placeholder="Your GitLab Username (optional)"
+          onChange={(e) => setGitlabUsername(e.target.value)}
+          value={gitlabUsername}
+          id="gitlab-username"
+          autoCorrect="off"
+          autoCapitalize="none"
+        />
+        <input
+          type="password"
+          placeholder="GitLab Access Token (optional)"
+          onChange={(e) => setGitlabToken(e.target.value)}
+          value={gitlabToken}
+          id="gitlab-token"
+          autoComplete="off"
+          autoCorrect="off"
+          autoCapitalize="none"
+        />
         <button type="submit" disabled={username.length <= 0 || loading}>
           <span role="img" aria-label="Stars">
             ✨
diff --git a/src/styles/App.css b/src/styles/App.css
index 63b5702..37e1a1b 100644
--- a/src/styles/App.css
+++ b/src/styles/App.css
@@ -116,13 +116,14 @@ h6 {
 form {
   margin: 2em 0 1em;
   display: flex;
+  flex-direction: column;
   justify-content: center;
   align-items: center;
+  gap: 0.5rem;
 }
 
 input {
   border: 0.1rem solid var(--input-border);
-  border-right: 0;
   border-radius: 0.4rem;
   padding: 0.6rem 1rem;
   height: 4rem;
@@ -156,13 +157,11 @@ button:disabled {
   cursor: not-allowed;
 }
 
-form input {
-  width: 30rem;
-  border-radius: 0.4rem 0 0 0.4rem;
-}
-
+form input,
 form button {
-  border-radius: 0 0.4rem 0.4rem 0;
+  width: 30rem;
+  max-width: 100%;
+  border-radius: 0.4rem;
 }
 
 .App-buttons {
@@ -261,7 +260,6 @@ footer a {
   }
 
   form input {
-    margin-bottom: 0.5rem;
     text-align: center;
   }
 
@@ -276,10 +274,6 @@ footer a {
     text-align: center;
   }
 
-  form input {
-    flex: 1;
-  }
-
   .App-themes-list {
     display: flex;
     flex-wrap: wrap;
diff --git a/src/utils/api/fetch.js b/src/utils/api/fetch.js
index 187a917..25da92d 100644
--- a/src/utils/api/fetch.js
+++ b/src/utils/api/fetch.js
@@ -1,5 +1,6 @@
 import cheerio from "cheerio";
 import _ from "lodash";
+import { fetchGitlabContributions } from "./gitlab";
 
 const COLOR_MAP = {
   0: "#ebedf0",
@@ -33,7 +34,15 @@ async function fetchYears(username) {
     });
 }
 
-async function fetchDataForYear(url, year, format) {
+// GitHub uses 4 levels, the intensity of a day is calculated relative to the
+// busiest day of the year
+function intensityForCount(count, maxCount) {
+  if (count <= 0) return 0;
+  if (maxCount <= 0) return 0;
+  return Math.min(4, Math.ceil((count / maxCount) * 4));
+}
+
+async function fetchDataForYear(url, year, format, gitlabContributions = {}) {
   const data = await fetch(`https://github.com${url}`, {
     headers: {
       "x-requested-with": "XMLHttpRequest"
@@ -53,47 +62,63 @@ async function fetchDataForYear(url, year, format) {
     [contribCount] = contribText;
     contribCount = parseInt(contribCount.replace(/,/g, ""), 10);
   }
+  const parseDay = (day) => {
+    const $day = $(day);
+    const dateString = $day.attr("data-date");
+    const date = dateString.split("-").map((d) => parseInt(d, 10));
+    let dayCount = 0;
+    try {
+      const idContributionCount = $day.attr("id");
+      const contributionsText = $('[for="' + idContributionCount + '"]').text();
+      const match = contributionsText.match(/^(\d+) contribution.*\.$/);
+      dayCount = parseInt(match[1], 10);
+    } catch (e) {
+      // pass
+      dayCount = 0;
+    }
+
+    const gitlabCount = gitlabContributions[dateString] || 0;
+    dayCount += gitlabCount;
+
+    const value = {
+      date: dateString,
+      count: dayCount,
+      gitlabCount,
+      color: COLOR_MAP[$day.attr("data-level")],
+      intensity: $day.attr("data-level") || 0
+    };
+    return { date, value };
+  };
+
+  const days = $days.get().map((day) => parseDay(day));
+  const gitlabTotal = days.reduce((sum, { value }) => sum + value.gitlabCount, 0);
+
+  // the levels reported by GitHub don't know about the GitLab contributions,
+  // so they have to be recalculated as soon as there are any
+  if (gitlabTotal > 0) {
+    const maxCount = days.reduce(
+      (max, { value }) => Math.max(max, value.count),
+      0
+    );
+    days.forEach(({ value }) => {
+      value.intensity = intensityForCount(value.count, maxCount);
+      value.color = COLOR_MAP[value.intensity];
+    });
+  }
+
   return {
     year,
-    total: contribCount || 0,
+    total: (contribCount || 0) + gitlabTotal,
     range: {
       start: $($days.get(0)).attr("data-date"),
       end: $($days.get($days.length - 1)).attr("data-date")
     },
     contributions: (() => {
-      const parseDay = (day, index) => {
-        const $day = $(day);
-        const date = $day
-          .attr("data-date")
-          .split("-")
-          .map((d) => parseInt(d, 10));
-        const color = COLOR_MAP[$day.attr("data-level")];
-        const idContributionCount = $day.attr("id")
-        contribCount = 0
-        try {
-          const contributionsText = $('[for="' + idContributionCount + '"]').text()
-          const match = contributionsText.match(/^(\d+) contribution.*\.$/);
-          contribCount = parseInt(match[1], 10);
-        } catch (e) {
-          // pass
-          contribCount = 0
-        }
-
-        const value = {
-          date: $day.attr("data-date"),
-          count: contribCount,
-          color,
-          intensity: $day.attr("data-level") || 0
-        };
-        return { date, value };
-      };
-
       if (format !== "nested") {
-        return $days.get().map((day, index) => parseDay(day, index).value);
+        return days.map(({ value }) => value);
       }
 
-      return $days.get().reduce((o, day, index) => {
-        const { date, value } = parseDay(day, index);
+      return days.reduce((o, { date, value }) => {
         const [y, m, d] = date;
         if (!o[y]) o[y] = {};
         if (!o[y][m]) o[y][m] = {};
@@ -104,10 +129,21 @@ async function fetchDataForYear(url, year, format) {
   };
 }
 
-export async function fetchDataForAllYears(username, format) {
-  const years = await fetchYears(username);
+export async function fetchDataForAllYears(
+  username,
+  format,
+  gitlabUsername,
+  gitlabUrl,
+  gitlabToken
+) {
+  const [years, gitlabContributions] = await Promise.all([
+    fetchYears(username),
+    fetchGitlabContributions(gitlabUsername, gitlabUrl, gitlabToken)
+  ]);
   return Promise.all(
-    years.map((year) => fetchDataForYear(year.href, year.text, format))
+    years.map((year) =>
+      fetchDataForYear(year.href, year.text, format, gitlabContributions)
+    )
   ).then((resp) => {
     return {
       years: (() => {
diff --git a/src/utils/api/gitlab.js b/src/utils/api/gitlab.js
new file mode 100644
index 0000000..d2d062f
--- /dev/null
+++ b/src/utils/api/gitlab.js
@@ -0,0 +1,39 @@
+/**
+ * Fetches the contribution calendar of a user on a (private) GitLab instance.
+ *
+ * The GitLab instance URL, the username and (for private instances) a personal
+ * access token with the `read_user` scope are entered in the form of the app
+ * and passed to the API route, they are not read from any configuration file.
+ */
+
+/**
+ * @returns {Promise<Object>} map of `YYYY-MM-DD` -> number of contributions
+ */
+export async function fetchGitlabContributions(username, gitlabUrl, gitlabToken) {
+  if (!username || !gitlabUrl) {
+    return {};
+  }
+
+  const baseUrl = gitlabUrl.trim().replace(/\/+$/, "");
+  const url = `${baseUrl}/users/${encodeURIComponent(
+    username
+  )}/calendar.json`;
+
+  const headers = { accept: "application/json" };
+  if (gitlabToken) {
+    headers["PRIVATE-TOKEN"] = gitlabToken;
+  }
+
+  const response = await fetch(url, { headers });
+  if (!response.ok) {
+    throw new Error(
+      `Could not fetch GitLab contributions of "${username}" (${response.status})`
+    );
+  }
+
+  const calendar = await response.json();
+  return Object.entries(calendar).reduce((counts, [date, count]) => {
+    counts[date] = parseInt(count, 10) || 0;
+    return counts;
+  }, {});
+}
diff --git a/src/utils/export.js b/src/utils/export.js
index acca783..7f6ebb1 100644
--- a/src/utils/export.js
+++ b/src/utils/export.js
@@ -2,8 +2,21 @@ import { toast } from "react-hot-toast";
 
 const API_URL = "/api/v1/";
 
-export function fetchData(username) {
-  return fetch(API_URL + username).then((res) => res.json());
+export function fetchData(username, gitlab = {}) {
+  const { username: gitlabUsername, url: gitlabUrl, token: gitlabToken } = gitlab;
+  const params = new URLSearchParams();
+  if (gitlabUsername && gitlabUrl) {
+    params.set("gitlabUsername", gitlabUsername);
+    params.set("gitlabUrl", gitlabUrl);
+  }
+  const query = params.toString() ? `?${params.toString()}` : "";
+  const headers = {};
+  if (gitlabToken) {
+    headers["x-gitlab-token"] = gitlabToken;
+  }
+  return fetch(API_URL + username + query, { headers }).then((res) =>
+    res.json()
+  );
 }
 
 export function download(canvas) {
@@ -83,3 +96,11 @@ export async function copyToClipboard(canvas) {
 export function cleanUsername(username) {
   return username.replace(/^(http|https):\/\/(?!www\.)github\.com\//, "");
 }
+
+export function cleanGitlabUsername(username) {
+  return username.trim().replace(/^(http|https):\/\/[^/]+\//, "");
+}
+
+export function cleanGitlabUrl(url) {
+  return url.trim().replace(/\/+$/, "");
+}