diff --git a/src/app-helpers.js b/src/app-helpers.js
index 8531de8..9cebad2 100644
--- a/src/app-helpers.js
+++ b/src/app-helpers.js
@@ -127,8 +127,8 @@ export function useLanguageLoader(path) {
   }, [path]);
 }
 
-export function useCommitsFetcher({ repo, sha, path }) {
-  return useLoader(async () => getCommits(repo, sha, path), [repo, sha, path]);
+export function useCommitsFetcher({ repo, path }) {
+  return useLoader(async () => getCommits(repo, path), [repo, path]);
 }
 
 export function useDocumentTitle(title) {
@@ -138,20 +138,15 @@ export function useDocumentTitle(title) {
 }
 
 export function getUrlParams() {
-  const [
-    ,
-    owner,
-    reponame,
-    action,
-    sha,
-    ...paths
-  ] = window.location.pathname.split("/");
+  const [, owner, reponame, action, ...paths] = window.location.pathname.split(
+    "/"
+  );
 
   if (action !== "commits" && action !== "blob") {
     return [];
   }
 
-  return [owner + "/" + reponame, sha, "/" + paths.join("/")];
+  return [owner + "/" + reponame, "/" + paths.join("/")];
 }
 
 function login() {
diff --git a/src/app.js b/src/app.js
index 3407bf9..78d6984 100644
--- a/src/app.js
+++ b/src/app.js
@@ -17,12 +17,12 @@ export default function App() {
     return <CliApp data={cli} />;
   }
 
-  const [repo, sha, path] = getUrlParams();
+  const [repo, path] = getUrlParams();
 
   if (!repo) {
     return <Landing />;
   } else {
-    return <GitHubApp repo={repo} sha={sha} path={path} />;
+    return <GitHubApp repo={repo} path={path} />;
   }
 }
 
diff --git a/src/github.js b/src/github.js
index ba4f486..2353064 100644
--- a/src/github.js
+++ b/src/github.js
@@ -25,9 +25,37 @@ async function getContent(repo, sha, path) {
   return { content, url: contentJson.html_url };
 }
 
-export async function getCommits(repo, sha, path, top = 10) {
+async function splitBranchAndFilePath(repo, path) {
+  const branchesResponse = await fetch(
+    `https://api.github.com/repos/${repo}/branches`,
+    { headers: getHeaders() }
+  );
+
+  const branchesJson = await branchesResponse.json();
+  const branchNames = branchesJson
+    .map(branch => branch.name)
+    .sort(function(a, b) {
+      // Sort by length so that the longest string is always tried first.
+      // That way we won't remove any substrings by accident.
+      return b.length - a.length;
+    });
+
+  let branchName = "master";
+  let filePath = path;
+  branchNames.forEach(branch => {
+    if (path.startsWith("/" + branch)) {
+      branchName = branch;
+      filePath = path.replace("/" + branch + "/", "");
+    }
+  });
+  return { branchName, filePath };
+}
+
+export async function getCommits(repo, path, top = 10) {
+  const { branchName, filePath } = await splitBranchAndFilePath(repo, path);
+
   const commitsResponse = await fetch(
-    `https://api.github.com/repos/${repo}/commits?sha=${sha}&path=${path}`,
+    `https://api.github.com/repos/${repo}/commits?sha=${branchName}&path=${filePath}`,
     { headers: getHeaders() }
   );
   if (!commitsResponse.ok) {
@@ -55,7 +83,7 @@ export async function getCommits(repo, sha, path, top = 10) {
 
   await Promise.all(
     commits.map(async commit => {
-      const info = await getContent(repo, commit.sha, path);
+      const info = await getContent(repo, commit.sha, filePath);
       commit.content = info.content;
       commit.fileUrl = info.url;
     })