diff --git a/backend/js/src/main/scala/eu/joaocosta/minart/backend/JsResource.scala b/backend/js/src/main/scala/eu/joaocosta/minart/backend/JsResource.scala
index 6c622471..6c1da5bd 100644
--- a/backend/js/src/main/scala/eu/joaocosta/minart/backend/JsResource.scala
+++ b/backend/js/src/main/scala/eu/joaocosta/minart/backend/JsResource.scala
@@ -1,12 +1,13 @@
 package eu.joaocosta.minart.backend
 
-import java.io.{ByteArrayInputStream, InputStream}
+import java.io.{ByteArrayInputStream, ByteArrayOutputStream, InputStream, OutputStream}
 
 import scala.concurrent.{Future, Promise}
 import scala.io.Source
 import scala.scalajs.js
-import scala.util.Try
+import scala.util.{Try, Using}
 
+import org.scalajs.dom
 import org.scalajs.dom.{ProgressEvent, XMLHttpRequest}
 
 import eu.joaocosta.minart.runtime.Resource
@@ -16,22 +17,35 @@ import eu.joaocosta.minart.runtime.Resource
 final case class JsResource(resourcePath: String) extends Resource {
   def path = "./" + resourcePath
 
+  private def loadFromLocalStorage(): Option[String] =
+    Option(dom.window.localStorage.getItem(resourcePath))
+
   def withSource[A](f: Source => A): Try[A] = Try {
-    val xhr = new XMLHttpRequest()
-    xhr.open("GET", path, false)
-    xhr.send()
-    f(Source.fromString(xhr.responseText))
+    val data = loadFromLocalStorage() match {
+      case Some(d) => d
+      case None =>
+        val xhr = new XMLHttpRequest()
+        xhr.open("GET", path, false)
+        xhr.send()
+        xhr.responseText
+    }
+    f(Source.fromString(data))
   }
 
   def withSourceAsync[A](f: Source => A): Future[A] = {
     val promise = Promise[A]()
-    val xhr     = new XMLHttpRequest()
-    xhr.open("GET", path)
-    xhr.onloadend = (event: ProgressEvent) => {
-      if (xhr.status != 200) promise.failure(new Exception(xhr.statusText))
-      else promise.complete(Try(f(Source.fromString(xhr.responseText))))
+    loadFromLocalStorage() match {
+      case Some(data) =>
+        promise.complete(Try(f(Source.fromString(data))))
+      case None =>
+        val xhr = new XMLHttpRequest()
+        xhr.open("GET", path)
+        xhr.onloadend = (event: ProgressEvent) => {
+          if (xhr.status != 200) promise.failure(new Exception(xhr.statusText))
+          else promise.complete(Try(f(Source.fromString(xhr.responseText))))
+        }
+        xhr.send()
     }
-    xhr.send()
     promise.future
   }
 
@@ -41,22 +55,39 @@ final case class JsResource(resourcePath: String) extends Resource {
 
   def withInputStreamAsync[A](f: InputStream => A): Future[A] = {
     val promise = Promise[A]()
-    val xhr     = new XMLHttpRequest()
-    xhr.open("GET", path)
-    xhr.overrideMimeType("text/plain; charset=x-user-defined")
-    xhr.onloadend = (event: ProgressEvent) => {
-      if (xhr.status != 200) promise.failure(new Exception(xhr.statusText))
-      else promise.complete(Try(f(new ByteArrayInputStream(xhr.responseText.toCharArray.map(_.toByte)))))
+    loadFromLocalStorage() match {
+      case Some(data) =>
+        val is = new ByteArrayInputStream(data.toCharArray.map(_.toByte))
+        promise.complete(Try(f(is)))
+      case None =>
+        val xhr = new XMLHttpRequest()
+        xhr.open("GET", path)
+        xhr.overrideMimeType("text/plain; charset=x-user-defined")
+        xhr.onloadend = (event: ProgressEvent) => {
+          if (xhr.status != 200) promise.failure(new Exception(xhr.statusText))
+          else promise.complete(Try(f(new ByteArrayInputStream(xhr.responseText.toCharArray.map(_.toByte)))))
+        }
+        xhr.send()
     }
-    xhr.send()
     promise.future
   }
 
   def unsafeInputStream(): InputStream = {
-    val xhr = new XMLHttpRequest()
-    xhr.open("GET", path, false)
-    xhr.overrideMimeType("text/plain; charset=x-user-defined")
-    xhr.send()
-    new ByteArrayInputStream(xhr.responseText.toCharArray.map(_.toByte))
+    val data = loadFromLocalStorage() match {
+      case Some(d) => d
+      case None =>
+        val xhr = new XMLHttpRequest()
+        xhr.open("GET", path, false)
+        xhr.overrideMimeType("text/plain; charset=x-user-defined")
+        xhr.send()
+        xhr.responseText
+    }
+    new ByteArrayInputStream(data.toCharArray.map(_.toByte))
   }
+
+  def withOutputStream(f: OutputStream => Unit): Unit =
+    Using[ByteArrayOutputStream, Unit](new ByteArrayOutputStream()) { os =>
+      f(os)
+      dom.window.localStorage.setItem(resourcePath, os.toByteArray().iterator.map(_.toChar).mkString(""))
+    }
 }
diff --git a/backend/jvm/src/main/scala/eu/joaocosta/minart/backend/JavaResource.scala b/backend/jvm/src/main/scala/eu/joaocosta/minart/backend/JavaResource.scala
index 93f4046d..2778e80c 100644
--- a/backend/jvm/src/main/scala/eu/joaocosta/minart/backend/JavaResource.scala
+++ b/backend/jvm/src/main/scala/eu/joaocosta/minart/backend/JavaResource.scala
@@ -1,6 +1,6 @@
 package eu.joaocosta.minart.backend
 
-import java.io.{FileInputStream, InputStream}
+import java.io.{FileInputStream, FileOutputStream, InputStream, OutputStream}
 
 import scala.concurrent._
 import scala.io.Source
@@ -23,10 +23,7 @@ final case class JavaResource(resourcePath: String) extends Resource {
   def path = "./" + resourcePath
   def withSource[A](f: Source => A): Try[A] = {
     Using[Source, A](
-      Source.fromInputStream(
-        Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get)
-          .getOrElse(new FileInputStream(path))
-      )
+      Source.fromInputStream(unsafeInputStream())
     )(f)
   }
   def withSourceAsync[A](f: Source => A): Future[A] = Future(blocking(withSource(f)).get)
@@ -36,5 +33,8 @@ final case class JavaResource(resourcePath: String) extends Resource {
 
   // TODO use Try(Source.fromResource(resourcePath)).getOrElse(Source.fromFile(path)) on scala 2.12+
   def unsafeInputStream(): InputStream =
-    Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get).getOrElse(new FileInputStream(path))
+    Try(new FileInputStream(path)).orElse(Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get)).get
+
+  def withOutputStream(f: OutputStream => Unit): Unit =
+    Using[OutputStream, Unit](new FileOutputStream(path))(f)
 }
diff --git a/backend/native/src/main/scala/eu/joaocosta/minart/backend/NativeResource.scala b/backend/native/src/main/scala/eu/joaocosta/minart/backend/NativeResource.scala
index 56f19382..ae1fe63f 100644
--- a/backend/native/src/main/scala/eu/joaocosta/minart/backend/NativeResource.scala
+++ b/backend/native/src/main/scala/eu/joaocosta/minart/backend/NativeResource.scala
@@ -1,6 +1,6 @@
 package eu.joaocosta.minart.backend
 
-import java.io.{FileInputStream, InputStream}
+import java.io.{FileInputStream, FileOutputStream, InputStream, OutputStream}
 
 import scala.concurrent.Future
 import scala.io.Source
@@ -24,10 +24,7 @@ final case class NativeResource(resourcePath: String) extends Resource {
   def path = "./" + resourcePath
   def withSource[A](f: Source => A): Try[A] = {
     Using[Source, A](
-      Source.fromInputStream(
-        Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get)
-          .getOrElse(new FileInputStream(path))
-      )
+      Source.fromInputStream(unsafeInputStream())
     )(f)
   }
   def withSourceAsync[A](f: Source => A): Future[A] =
@@ -35,7 +32,11 @@ final case class NativeResource(resourcePath: String) extends Resource {
   def withInputStream[A](f: InputStream => A): Try[A] = Using[InputStream, A](unsafeInputStream())(f)
   def withInputStreamAsync[A](f: InputStream => A): Future[A] =
     Future.fromTry(withInputStream(f))
+
   // TODO use Try(Source.fromResource(resourcePath)).getOrElse(Source.fromFile(path)) on scala 2.12+
   def unsafeInputStream(): InputStream =
-    Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get).getOrElse(new FileInputStream(path))
+    Try(new FileInputStream(path)).orElse(Try(Option(this.getClass().getResourceAsStream("/" + resourcePath)).get)).get
+
+  def withOutputStream(f: OutputStream => Unit): Unit =
+    Using[OutputStream, Unit](new FileOutputStream(path))(f)
 }
diff --git a/core/shared/src/main/scala/eu/joaocosta/minart/runtime/Resource.scala b/core/shared/src/main/scala/eu/joaocosta/minart/runtime/Resource.scala
index 7219dd09..2e5527c6 100644
--- a/core/shared/src/main/scala/eu/joaocosta/minart/runtime/Resource.scala
+++ b/core/shared/src/main/scala/eu/joaocosta/minart/runtime/Resource.scala
@@ -1,6 +1,6 @@
 package eu.joaocosta.minart.runtime
 
-import java.io.InputStream
+import java.io.{InputStream, OutputStream}
 
 import scala.concurrent.Future
 import scala.io.Source
@@ -44,6 +44,11 @@ trait Resource {
     * This method should only be used if for some reason the input stream must stay open (e.g. for data streaming)
     */
   def unsafeInputStream(): InputStream
+
+  /** Provides a [[java.io.OutputStream]] to write data to this resource location.
+    * The OutputStream is closed in the end, so it should not escape this call.
+    */
+  def withOutputStream(f: OutputStream => Unit): Unit
 }
 
 object Resource {