diff --git a/package.json b/package.json
index 742ea5a1..384c69a1 100644
--- a/package.json
+++ b/package.json
@@ -42,6 +42,7 @@
     "firebase": "^5.5.8",
     "firebase-admin": "^6.3.0",
     "fontkit": "^1.7.7",
+    "get-folder-size": "^2.0.0",
     "glob": "^7.1.3",
     "got": "^9.3.2",
     "graphql": "^14.0.2",
diff --git a/readme.md b/readme.md
index de7b907b..72e505fa 100644
--- a/readme.md
+++ b/readme.md
@@ -63,7 +63,9 @@ require('@zeit/ncc')('/path/to/input', {
   minify: true, // default
   // externals to leave as requires of the build
   externals: ["externalpackage"],
-  sourceMap: true // default
+  sourceMap: true, // default
+  // provide a custom cache path or disable caching
+  cache: "./custom/cache/path" | false 
 }).then(({ code, assets }) => {
   console.log(code);
   // assets is an object of asset file names to sources
diff --git a/src/cli.js b/src/cli.js
index 9ea60174..1a2b3a83 100755
--- a/src/cli.js
+++ b/src/cli.js
@@ -2,14 +2,16 @@ const { resolve, relative, dirname, sep } = require("path");
 const glob = require("glob");
 const shebangRegEx = require("./utils/shebang");
 const rimraf = require("rimraf");
+const crypto = require("crypto");
+const fs = require("fs");
+const mkdirp = require("mkdirp");
 
 const usage = `Usage: ncc <cmd> <opts>
 
 Commands:
   build <input-file> [opts]
   run <input-file> [opts]
-  cache clean
-  cache dir
+  cache clean|dir|size
   help
   version
 
@@ -17,6 +19,7 @@ Options:
   -o, --out [file]      Output directory for build (defaults to dist)
   -M, --no-minify       Skip output minification
   -S, --no-source-map   Skip source map output
+  -C, --no-cache        Skip build cache population
   -e, --external [mod]  Skip bundling 'mod'. Can be used many times
   -q, --quiet           Disable build summaries / non-error outputs
 `;
@@ -29,6 +32,8 @@ try {
     "-e": "--external",
     "--out": String,
     "-o": "--out",
+    "--no-cache": Boolean,
+    "-C": "--no-cache",
     "--no-minify": Boolean,
     "-M": "--no-minify",
     "--no-source-map": Boolean,
@@ -106,14 +111,27 @@ switch (args._[0]) {
       errFlagNotCompatible(flags[0], "cache");
 
     const cacheDir = require("./utils/ncc-cache-dir");
-    if (args._[1] === "dir") {
-      console.log(cacheDir);
-    }
-    else if (args._[1] === "clear") {
-      rimraf.sync(cacheDir);
-    }
-    else {
-      errInvalidCommand("cache " + args._[1]);
+    switch (args._[1]) {
+      case "clean":
+        rimraf.sync(cacheDir);
+      break;
+      case "dir":
+        console.log(cacheDir);
+      break;
+      case "size":
+        require("get-folder-size")(cacheDir, (err, size) => {
+          if (err) {
+            if (err.code === 'ENOENT') {
+              console.log("0MB");
+              return;
+            }
+            throw err;
+          }
+          console.log(`${(size / 1024 / 1024).toFixed(2)}MB`);
+        });
+      break;
+      default:
+        errInvalidCommand("cache " + args._[1]);
     }
 
   break;
@@ -126,10 +144,15 @@ switch (args._[0]) {
 
     outDir = resolve(
       require("os").tmpdir(),
-      Math.random()
-        .toString(16)
-        .substr(2)
+      crypto.createHash('md5').digest(resolve(args._[1] || ".")).toString('hex')
     );
+    if (fs.existsSync(outDir)) {
+      console.error(
+        `Error: Application at ${args._[1] || "."} is already running or didn't cleanup after previous run.` +
+        `To manually clear the last run build, try running "rm -rf ${outDir}".`
+      );
+      process.exit(1);
+    }
     run = true;
 
   // fallthrough
@@ -143,14 +166,13 @@ switch (args._[0]) {
       {
         minify: !args["--no-minify"] && !run,
         externals: args["--external"],
-        sourceMap: !args["--no-source-map"]
+        sourceMap: !args["--no-source-map"],
+        cacheDirectory: args["--no-cache"] ? false : undefined
       }
     );
     ncc.then(
       async ({ code, map, assets }) => {
         outDir = outDir || resolve("dist");
-        const fs = require("fs");
-        const mkdirp = require("mkdirp");
         mkdirp.sync(outDir);
         // remove all existing ".js" files in the out directory
         await Promise.all(
diff --git a/src/index.js b/src/index.js
index 5c5ca63c..d8bfdb21 100644
--- a/src/index.js
+++ b/src/index.js
@@ -35,10 +35,11 @@ function resolveModule(context, request, callback, forcedExternals = []) {
 module.exports = async (
   entry,
   {
+    cache,
     externals = [],
+    filename = "index.js",
     minify = false,
-    sourceMap = false,
-    filename = "index.js"
+    sourceMap = false
   } = {}
 ) => {
   const shebangMatch = fs.readFileSync(resolve.sync(entry)).toString().match(shebangRegEx);
@@ -47,9 +48,9 @@ module.exports = async (
   const assets = Object.create(null);
   const compiler = webpack({
     entry,
-    cache: {
+    cache: cache === false ? undefined : {
       type: "filesystem",
-      cacheDirectory: nccCacheDir,
+      cacheDirectory: typeof cache === 'string' ? cache : nccCacheDir,
       name: "ncc",
       version: require('../package.json').version,
       store: "instant"
diff --git a/yarn.lock b/yarn.lock
index 1cb80c0c..ea0bf516 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4122,6 +4122,11 @@ functional-red-black-tree@^1.0.1:
   resolved "https://registry.yarnpkg.com/functional-red-black-tree/-/functional-red-black-tree-1.0.1.tgz#1b0ab3bd553b2a0d6399d29c0e3ea0b252078327"
   integrity sha1-GwqzvVU7Kg1jmdKcDj6gslIHgyc=
 
+gar@^1.0.2:
+  version "1.0.3"
+  resolved "https://registry.yarnpkg.com/gar/-/gar-1.0.3.tgz#cd6e954dff11821697a9ed5852c7ac5f18df02ce"
+  integrity sha512-zDpwk/l3HbhjVAvdxNUTJFzgXiNy0a7EmE/50XT38o1z+7NJbFhp+8CDsv1Qgy2adBAwUVYlMpIX2fZUbmlUJw==
+
 gauge@~2.7.3:
   version "2.7.4"
   resolved "https://registry.yarnpkg.com/gauge/-/gauge-2.7.4.tgz#2c03405c7538c39d7eb37b317022e325fb018bf7"
@@ -4189,6 +4194,14 @@ get-caller-file@^1.0.1:
   resolved "https://registry.yarnpkg.com/get-caller-file/-/get-caller-file-1.0.3.tgz#f978fa4c90d1dfe7ff2d6beda2a515e713bdcf4a"
   integrity sha512-3t6rVToeoZfYSGd8YoLFR2DJkiQrIiUrGcjvFX2mDw3bn6k2OtwHN0TNCLbBO+w8qTvimhDkv+LSscbJY1vE6w==
 
+get-folder-size@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/get-folder-size/-/get-folder-size-2.0.0.tgz#f0ecb4aa30ea855e051366714eaabcc41cf9d43f"
+  integrity sha512-5h4efQY/sHvf9ZuwOan1HgNaRyApKnJjZ1ZdTOPkpTjIHZNqeMTabBU/LLN6lU9jncBwxJKFcG9cuqiGhu47uQ==
+  dependencies:
+    gar "^1.0.2"
+    tiny-each-async "2.0.3"
+
 get-stdin@^5.0.1:
   version "5.0.1"
   resolved "https://registry.yarnpkg.com/get-stdin/-/get-stdin-5.0.1.tgz#122e161591e21ff4c52530305693f20e6393a398"
@@ -10446,6 +10459,11 @@ timm@^1.6.1:
   resolved "https://registry.yarnpkg.com/timm/-/timm-1.6.1.tgz#5f8aafc932248c76caf2c6af60542a32d3c30701"
   integrity sha512-hqDTYi/bWuDxL2i6T3v6nrvkAQ/1Bc060GSkVEQZp02zTSTB4CHSKsOkliequCftQaNRcjRqUZmpGWs5FfhrNg==
 
+tiny-each-async@2.0.3:
+  version "2.0.3"
+  resolved "https://registry.yarnpkg.com/tiny-each-async/-/tiny-each-async-2.0.3.tgz#8ebbbfd6d6295f1370003fbb37162afe5a0a51d1"
+  integrity sha1-jru/1tYpXxNwAD+7NxYq/loKUdE=
+
 tiny-inflate@^1.0.0, tiny-inflate@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/tiny-inflate/-/tiny-inflate-1.0.2.tgz#93d9decffc8805bd57eae4310f0b745e9b6fb3a7"