Code editor bookmarklets. Just copy the code and paste it in the browser URL. It will load ACE editor with the mode you choose for the language.

README.md

Available modes: abap, ada, actionscript, asciidoc, assembly_x86, autohotkey, batchfile, c9search, c_cpp, clojure, cobol, coffee, coldfusion, csharp, css, curly, d, dart, diff, dot, erlang, ejs, forth, ftl, glsl, golang, groovy, haml, haskell, haxe, html, html_ruby, ini, jade, java, javascript, json, jsoniq, jsp, jsx, julia, latex, less, liquid, lisp, livescript, logiql, lsl, lua, luapage, lucene, makefile, matlab, markdown, mysql, mushcode, objectivec, ocaml, pascal, perl, pgsql, php, powershell, prolog, properties, python, r, rdoc, rhtml, ruby, rust, sass, scad, scala, scheme, scss, sh, snippets, sql, stylus, svg, tcl, tex, text, textile, toml, twig, typescript, vbscript, velocity, xml, xquery, yaml.

Available themes: eclipse, github, textmate, ambiance, dawn, chaos, chrome, dreamweaver, xcode, vibrant_ink, solarized_dark, solarized_light, tomorrow, tomorrow_night, tomorrow_night_blue, twilight, tomorrow_night_eighties, pastel_on_dark.

JS

data:text/html, <style type="text/css">#e{position:absolute;top:0;right:0;bottom:0;left:0;}</style><div id="e"></div><script src="http://d1n0x3qji82z53.cloudfront.net/src-min-noconflict/ace.js" type="text/javascript" charset="utf-8"></script><script>var e=ace.edit("e");e.setTheme("ace/theme/monokai");e.getSession().setMode("ace/mode/javascript");</script>

PHP

data:text/html, <style type="text/css">#e{position:absolute;top:0;right:0;bottom:0;left:0;}</style><div id="e"></div><script src="http://d1n0x3qji82z53.cloudfront.net/src-min-noconflict/ace.js" type="text/javascript" charset="utf-8"></script><script>var e=ace.edit("e");e.setTheme("ace/theme/monokai");e.getSession().setMode("ace/mode/php");</script>

Python

data:text/html, <style type="text/css">#e{position:absolute;top:0;right:0;bottom:0;left:0;}</style><div id="e"></div><script src="http://d1n0x3qji82z53.cloudfront.net/src-min-noconflict/ace.js" type="text/javascript" charset="utf-8"></script><script>var e=ace.edit("e");e.setTheme("ace/theme/monokai");e.getSession().setMode("ace/mode/python");</script>