diff --git a/mitmproxy/contentviews/__init__.py b/mitmproxy/contentviews/__init__.py
index 3857d5e59..357172e3e 100644
--- a/mitmproxy/contentviews/__init__.py
+++ b/mitmproxy/contentviews/__init__.py
@@ -22,7 +22,7 @@ from mitmproxy import exceptions
 from mitmproxy.net import http
 from mitmproxy.utils import strutils
 from . import (
-    auto, raw, hex, json, html_outline, wbxml, javascript, css,
+    auto, raw, hex, json, xml_html, html_outline, wbxml, javascript, css,
     urlencoded, multipart, image, query, protobuf
 )
 from .base import View, VIEW_CUTOFF, KEY_MAX, format_text, format_dict
@@ -163,6 +163,7 @@ add(auto.ViewAuto())
 add(raw.ViewRaw())
 add(hex.ViewHex())
 add(json.ViewJSON())
+add(xml_html.ViewXmlHtml())
 add(wbxml.ViewWBXML())
 add(html_outline.ViewHTMLOutline())
 add(javascript.ViewJavaScript())
diff --git a/mitmproxy/contentviews/xml_html.py b/mitmproxy/contentviews/xml_html.py
new file mode 100644
index 000000000..0f2ce57df
--- /dev/null
+++ b/mitmproxy/contentviews/xml_html.py
@@ -0,0 +1,234 @@
+import io
+import re
+import textwrap
+from typing import Iterable
+
+from mitmproxy.contentviews import base
+from mitmproxy.utils import sliding_window
+
+"""
+A custom XML/HTML prettifier. Compared to other prettifiers, its main features are:
+
+- Implemented in pure Python.
+- Modifies whitespace only.
+- Works with any input.
+- Lazy evaluation.
+
+The implementation is split into two main parts: tokenization and formatting of tokens.
+"""
+
+# http://www.xml.com/pub/a/2001/07/25/namingparts.html - this is close enough for what we do.
+REGEX_TAG = re.compile("[a-zA-Z0-9._:\-]+(?!=)")
+# https://www.w3.org/TR/html5/syntax.html#void-elements
+HTML_VOID_ELEMENTS = {
+    "area", "base", "br", "col", "embed", "hr", "img", "input", "keygen", "link", "meta", "param",
+    "source", "track", "wbr"
+}
+NO_INDENT_TAGS = {"xml", "doctype", "html"}
+INDENT = 2
+
+
+class Token:
+    def __init__(self, data):
+        self.data = data
+
+    def __repr__(self):
+        return "{}({})".format(
+            type(self).__name__,
+            self.data
+        )
+
+
+class Text(Token):
+    @property
+    def text(self):
+        return self.data.strip()
+
+
+class Tag(Token):
+    @property
+    def tag(self):
+        t = REGEX_TAG.search(self.data)
+        if t is not None:
+            return t.group(0).lower()
+        return "<empty>"
+
+    @property
+    def is_comment(self) -> bool:
+        return self.data.startswith("<!--")
+
+    @property
+    def is_cdata(self) -> bool:
+        return self.data.startswith("<![CDATA[")
+
+    @property
+    def is_closing(self):
+        return self.data.startswith("</")
+
+    @property
+    def is_self_closing(self):
+        return self.is_comment or self.is_cdata or self.data.endswith(
+            "/>") or self.tag in HTML_VOID_ELEMENTS
+
+    @property
+    def is_opening(self):
+        return not self.is_closing and not self.is_self_closing
+
+    @property
+    def done(self):
+        if self.is_comment:
+            return self.data.endswith("-->")
+        elif self.is_cdata:
+            return self.data.endswith("]]>")
+        else:
+            # This fails for attributes that contain an unescaped ">"
+            return self.data.endswith(">")
+
+
+def tokenize(data: str) -> Iterable[Token]:
+    token = Text("")  # type: Token
+
+    i = 0
+
+    def readuntil(char, start, include=1):
+        nonlocal i
+        end = data.find(char, start)
+        if end == -1:
+            end = len(data)
+        ret = data[i:end + include]
+        i = end + include
+        return ret
+
+    while i < len(data):
+        if isinstance(token, Text):
+            token.data = readuntil("<", i, 0)
+            if token.text:
+                yield token
+            token = Tag("")
+        elif isinstance(token, Tag):
+            token.data += readuntil(">", i, 1)
+            if token.done:
+                yield token
+                token = Text("")
+    if token.data.strip():
+        yield token
+
+
+def indent_text(data: str, prefix: str) -> str:
+    # Add spacing to first line so that we dedent in cases like this:
+    # <li>This is
+    #     example text
+    #     over multiple lines
+    # </li>
+    dedented = textwrap.dedent(" " * 32 + data).strip()
+    return textwrap.indent(dedented, prefix[:32])
+
+
+def is_inline_text(a: Token, b: Token, c: Token) -> bool:
+    if isinstance(a, Tag) and isinstance(b, Text) and isinstance(c, Tag):
+        if a.is_opening and "\n" not in b.data and c.is_closing and a.tag == c.tag:
+            return True
+
+
+def is_inline(prev2: Token, prev1: Token, t: Token, next1: Token, next2: Token) -> bool:
+    if isinstance(t, Text):
+        return is_inline_text(prev1, t, next1)
+    elif isinstance(t, Tag):
+        if is_inline_text(prev2, prev1, t) or is_inline_text(t, next1, next2):
+            return True
+        if isinstance(next1, Tag) and t.is_opening and next1.is_closing and t.tag == next1.tag:
+                return True  # <div></div> (start tag)
+        if isinstance(prev1, Tag) and prev1.is_opening and t.is_closing and prev1.tag == t.tag:
+            return True  # <div></div> (end tag)
+
+
+class ElementStack:
+    """
+    Keep track of how deeply nested our document is.
+    """
+
+    def __init__(self):
+        self.open_tags = []
+        self.indent = ""
+
+    def push_tag(self, tag: str):
+        if len(self.open_tags) > 16:
+            return
+        self.open_tags.append(tag)
+        if tag not in NO_INDENT_TAGS:
+            self.indent += " " * INDENT
+
+    def pop_tag(self, tag: str):
+        if tag in self.open_tags:
+            remove_indent = 0
+            while True:
+                t = self.open_tags.pop()
+                if t not in NO_INDENT_TAGS:
+                    remove_indent += INDENT
+                if t == tag:
+                    break
+            self.indent = self.indent[:-remove_indent]
+        else:
+            pass  # this closing tag has no start tag. let's keep indentation as-is.
+
+
+def format_xml(tokens: Iterable[Token]) -> str:
+    out = io.StringIO()
+
+    context = ElementStack()
+
+    for prev2, prev1, token, next1, next2 in sliding_window.window(tokens, 2, 2):
+        if isinstance(token, Tag):
+            if token.is_opening:
+                out.write(indent_text(token.data, context.indent))
+
+                if not is_inline(prev2, prev1, token, next1, next2):
+                    out.write("\n")
+
+                context.push_tag(token.tag)
+            elif token.is_closing:
+                context.pop_tag(token.tag)
+
+                if is_inline(prev2, prev1, token, next1, next2):
+                    out.write(token.data)
+                else:
+                    out.write(indent_text(token.data, context.indent))
+                out.write("\n")
+
+            else:  # self-closing
+                out.write(indent_text(token.data, context.indent))
+                out.write("\n")
+        elif isinstance(token, Text):
+            if is_inline(prev2, prev1, token, next1, next2):
+                out.write(token.text)
+            else:
+                out.write(indent_text(token.data, context.indent))
+                out.write("\n")
+        else:  # pragma: no cover
+            raise RuntimeError()
+
+    return out.getvalue()
+
+
+class ViewXmlHtml(base.View):
+    name = "XML/HTML"
+    prompt = ("xml/html", "x")
+    content_types = ["text/xml", "text/html"]
+
+    def __call__(self, data, **metadata):
+        # TODO:
+        # We should really have the message text as str here,
+        # not the message content as bytes.
+        # https://github.com/mitmproxy/mitmproxy/issues/1662#issuecomment-266192578
+        data = data.decode("utf8", "xmlcharrefreplace")
+        tokens = tokenize(data)
+        # TODO:
+        # Performance: Don't render the whole document right away.
+        # Let's wait with this until we have a sequence-like interface,
+        # this thing is reasonably fast right now anyway.
+        pretty = base.format_text(format_xml(tokens))
+        if "html" in data.lower():
+            t = "HTML"
+        else:
+            t = "XML"
+        return t, pretty
diff --git a/test/mitmproxy/contentviews/test_html_outline.py b/test/mitmproxy/contentviews/test_html_outline.py
index d9ccc4068..9e664e523 100644
--- a/test/mitmproxy/contentviews/test_html_outline.py
+++ b/test/mitmproxy/contentviews/test_html_outline.py
@@ -6,4 +6,4 @@ def test_view_html_outline():
     v = full_eval(html_outline.ViewHTMLOutline())
     s = b"<html><br><br></br><p>one</p></html>"
     assert v(s)
-    assert v(b'\xfe')
\ No newline at end of file
+    assert v(b'\xfe')
diff --git a/test/mitmproxy/contentviews/test_xml_html.py b/test/mitmproxy/contentviews/test_xml_html.py
new file mode 100644
index 000000000..899ecfded
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html.py
@@ -0,0 +1,29 @@
+import pytest
+
+from mitmproxy.contentviews import xml_html
+from mitmproxy.test import tutils
+from . import full_eval
+
+data = tutils.test_data.push("mitmproxy/contentviews/test_xml_html_data/")
+
+
+def test_simple():
+    v = full_eval(xml_html.ViewXmlHtml())
+    assert v(b"foo") == ('XML', [[('text', 'foo')]])
+    assert v(b"<html></html>") == ('HTML', [[('text', '<html></html>')]])
+
+
+@pytest.mark.parametrize("filename", [
+    "simple.html",
+    "cdata.xml",
+    "comment.xml",
+    "inline.html",
+])
+def test_format_xml(filename):
+    path = data.path(filename)
+    with open(path) as f:
+        input = f.read()
+    with open(path.replace(".", "-formatted.")) as f:
+        expected = f.read()
+    tokens = xml_html.tokenize(input)
+    assert xml_html.format_xml(tokens) == expected
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/cdata-formatted.xml b/test/mitmproxy/contentviews/test_xml_html_data/cdata-formatted.xml
new file mode 100644
index 000000000..44a81a83e
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/cdata-formatted.xml
@@ -0,0 +1,10 @@
+<exampleOfACDATA>
+  <![CDATA[
+      Since this is a CDATA section
+        I can use all sorts of reserved characters
+      like > < " and &
+  or write things like
+      <foo></bar>
+      but my document is still well formed!
+  ]]>
+</exampleOfACDATA>
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/cdata.xml b/test/mitmproxy/contentviews/test_xml_html_data/cdata.xml
new file mode 100644
index 000000000..b4c5dfca1
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/cdata.xml
@@ -0,0 +1,10 @@
+<exampleOfACDATA>
+<![CDATA[
+    Since this is a CDATA section
+      I can use all sorts of reserved characters
+    like > < " and &
+or write things like
+    <foo></bar>
+    but my document is still well formed!
+]]>
+</exampleOfACDATA>
\ No newline at end of file
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/comment-formatted.xml b/test/mitmproxy/contentviews/test_xml_html_data/comment-formatted.xml
new file mode 100644
index 000000000..d0da66655
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/comment-formatted.xml
@@ -0,0 +1,10 @@
+<exampleOfAComment>
+  <!--
+        Since this is a comment
+          I can use all sorts of reserved characters
+        like > < " and &
+    or write things like
+        <foo></bar>
+        but my document is still well formed!
+  -->
+</exampleOfAComment>
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/comment.xml b/test/mitmproxy/contentviews/test_xml_html_data/comment.xml
new file mode 100644
index 000000000..3f54ddba7
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/comment.xml
@@ -0,0 +1,10 @@
+<exampleOfAComment>
+<!--
+      Since this is a comment
+        I can use all sorts of reserved characters
+      like > < " and &
+  or write things like
+      <foo></bar>
+      but my document is still well formed!
+-->
+</exampleOfAComment>
\ No newline at end of file
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/inline-formatted.html b/test/mitmproxy/contentviews/test_xml_html_data/inline-formatted.html
new file mode 100644
index 000000000..5253bf4ff
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/inline-formatted.html
@@ -0,0 +1,14 @@
+<html>
+<head>
+  <title>Test Page</title>
+</head>
+<body>
+  <p>
+    <i class="fa fa-alert"></i>
+    Some things should be
+    <b>inline</b>
+    , some things shouldn't!
+  </p>
+  <i class="fa fa-warning"/>
+</body>
+</html>
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/inline.html b/test/mitmproxy/contentviews/test_xml_html_data/inline.html
new file mode 100644
index 000000000..3e4b16b95
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/inline.html
@@ -0,0 +1,7 @@
+<html>
+<head><title>Test Page</title></head>
+<body>
+    <p><i class="fa fa-alert"></i>Some things should be <b>inline</b>, some things shouldn't!</p>
+    <i class="fa fa-warning"/>
+</body>
+</html>
\ No newline at end of file
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/simple-formatted.html b/test/mitmproxy/contentviews/test_xml_html_data/simple-formatted.html
new file mode 100644
index 000000000..234384281
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/simple-formatted.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <title>title</title>
+</head>
+<body>
+  <h1>Hello World</h1>
+  <!-- page content -->
+</body>
+</html>
diff --git a/test/mitmproxy/contentviews/test_xml_html_data/simple.html b/test/mitmproxy/contentviews/test_xml_html_data/simple.html
new file mode 100644
index 000000000..73e81a5e1
--- /dev/null
+++ b/test/mitmproxy/contentviews/test_xml_html_data/simple.html
@@ -0,0 +1 @@
+<!DOCTYPE html><html lang="en"><head><title>title</title></head><body><h1>Hello World</h1><!-- page content --></body></html>