Nom : Fiddler
Langue : anglais
System Requirements
Windows XP / 2K3 / Vista / 2K8 / Win7 / Win8
Microsoft .NET Framework v2.0 or later
8 megabytes disk space / 800mhz processor (Screams at 2.4ghz)
512 megabytes RAM (2GB+ highly recommended)

License : freeware

Description :
Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.
Fiddler is freeware and can debug traffic from virtually any application that supports a proxy, including Internet Explorer, Google Chrome, Apple Safari, Mozilla Firefox, Opera, and thousands more. You can also debug traffic from popular devices like Windows Phone, iPod/iPad, and others.

Pour moi, le meilleur outil d'analyse de traffic !! bien plus complet que n'importe quel plugin firefox ou autre,rien à configurer, tout fonctionne après l'installation. Possibilité de placer des points d'arrêt où l'on veut, très facile de modifier le contenu des réponses renvoyées, décodage de traffic https et j'en passe, j'utilise très souvent au boulot.

http://www.fiddler2.com
download : http://www.fiddler2.com/Fiddler2/version.asp