Deploys are hard and it can be frustrating to do them. Many bugs manifest themselves during deploys, especially when there are a large number of code changes. Now what if a deploy also goes out to millions of people at once? Here’s the story of how my team makes a deploy of that scale safely and with ease. Publishers on the web use a single JavaScript file, widgets.js, to embed Twitter content on
![How Twitter deploys its widgets JavaScript](https://cdn-ak-scissors.b.st-hatena.com/image/square/a7dfbba80c1b2e3d08e53178d335285f8dc68548/height=288;version=1;width=512/https%3A%2F%2Fcdn.cms-twdigitalassets.com%2Fcontent%2Fdam%2Fblog-twitter%2Fengineering%2Fen_us%2Fmain-template-assets%2FEng_EXPLORE_Pink.png.twimg.768.png)