{
  "title":"defer attribute for external scripts",
  "description":"The boolean defer attribute on script elements allows the external JavaScript file to run when the DOM is loaded, without delaying page load first.",
  "spec":"https://html.spec.whatwg.org/multipage/scripting.html#attr-script-defer",
  "status":"ls",
  "links":[
    {
      "url":"https://developer.mozilla.org/en/HTML/Element/script#Attributes",
      "title":"MDN Web Docs - Script Attributes"
    },
    {
      "url":"https://raw.github.com/phiggins42/has.js/master/detect/script.js#script-defer",
      "title":"has.js test"
    },
    {
      "url":"https://www.webplatform.org/docs/html/attributes/defer",
      "title":"WebPlatform Docs"
    },
    {
      "url":"http://www.growingwiththeweb.com/2014/02/async-vs-defer-attributes.html",
      "title":"async vs defer attributes"
    }
  ],
  "bugs":[
    {
      "description":"IE < 10 may interleave execution of scripts, [See the discussion](https://github.com/h5bp/lazyweb-requests/issues/42)."
    },
    {
      "description":"Google Chrome does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - [Chromium Issue #611136](https://bugs.chromium.org/p/chromium/issues/detail?id=611136), [Chromium Issue #874749](https://bugs.chromium.org/p/chromium/issues/detail?id=874749)"
    }
  ],
  "categories":[
    "DOM",
    "HTML5"
  ],
  "stats":{
    "ie":{
      "5.5":"a #1",
      "6":"a #1",
      "7":"a #1",
      "8":"a #1",
      "9":"a #1",
      "10":"y",
      "11":"y"
    },
    "edge":{
      "12":"y",
      "13":"y",
      "14":"y",
      "15":"y",
      "16":"y",
      "17":"y",
      "18":"y",
      "76":"y"
    },
    "firefox":{
      "2":"n",
      "3":"n",
      "3.5":"y #2",
      "3.6":"y #2",
      "4":"y #2",
      "5":"y #2",
      "6":"y #2",
      "7":"y #2",
      "8":"y #2",
      "9":"y #2",
      "10":"y #2",
      "11":"y #2",
      "12":"y #2",
      "13":"y #2",
      "14":"y #2",
      "15":"y #2",
      "16":"y #2",
      "17":"y #2",
      "18":"y #2",
      "19":"y #2",
      "20":"y #2",
      "21":"y #2",
      "22":"y #2",
      "23":"y #2",
      "24":"y #2",
      "25":"y #2",
      "26":"y #2",
      "27":"y #2",
      "28":"y #2",
      "29":"y #2",
      "30":"y #2",
      "31":"y",
      "32":"y",
      "33":"y",
      "34":"y",
      "35":"y",
      "36":"y",
      "37":"y",
      "38":"y",
      "39":"y",
      "40":"y",
      "41":"y",
      "42":"y",
      "43":"y",
      "44":"y",
      "45":"y",
      "46":"y",
      "47":"y",
      "48":"y",
      "49":"y",
      "50":"y",
      "51":"y",
      "52":"y",
      "53":"y",
      "54":"y",
      "55":"y",
      "56":"y",
      "57":"y",
      "58":"y",
      "59":"y",
      "60":"y",
      "61":"y",
      "62":"y",
      "63":"y",
      "64":"y",
      "65":"y",
      "66":"y",
      "67":"y",
      "68":"y",
      "69":"y",
      "70":"y",
      "71":"y"
    },
    "chrome":{
      "4":"n",
      "5":"n",
      "6":"n",
      "7":"n",
      "8":"y",
      "9":"y",
      "10":"y",
      "11":"y",
      "12":"y",
      "13":"y",
      "14":"y",
      "15":"y",
      "16":"y",
      "17":"y",
      "18":"y",
      "19":"y",
      "20":"y",
      "21":"y",
      "22":"y",
      "23":"y",
      "24":"y",
      "25":"y",
      "26":"y",
      "27":"y",
      "28":"y",
      "29":"y",
      "30":"y",
      "31":"y",
      "32":"y",
      "33":"y",
      "34":"y",
      "35":"y",
      "36":"y",
      "37":"y",
      "38":"y",
      "39":"y",
      "40":"y",
      "41":"y",
      "42":"y",
      "43":"y",
      "44":"y",
      "45":"y",
      "46":"y",
      "47":"y",
      "48":"y",
      "49":"y",
      "50":"y",
      "51":"y",
      "52":"y",
      "53":"y",
      "54":"y",
      "55":"y",
      "56":"y",
      "57":"y",
      "58":"y",
      "59":"y",
      "60":"y",
      "61":"y",
      "62":"y",
      "63":"y",
      "64":"y",
      "65":"y",
      "66":"y",
      "67":"y",
      "68":"y",
      "69":"y",
      "70":"y",
      "71":"y",
      "72":"y",
      "73":"y",
      "74":"y",
      "75":"y",
      "76":"y",
      "77":"y",
      "78":"y",
      "79":"y",
      "80":"y"
    },
    "safari":{
      "3.1":"n",
      "3.2":"n",
      "4":"n",
      "5":"y",
      "5.1":"y",
      "6":"y",
      "6.1":"y",
      "7":"y",
      "7.1":"y",
      "8":"y",
      "9":"y",
      "9.1":"y",
      "10":"y",
      "10.1":"y",
      "11":"y",
      "11.1":"y",
      "12":"y",
      "12.1":"y",
      "13":"y",
      "TP":"y"
    },
    "opera":{
      "9":"n",
      "9.5-9.6":"n",
      "10.0-10.1":"n",
      "10.5":"n",
      "10.6":"n",
      "11":"n",
      "11.1":"n",
      "11.5":"n",
      "11.6":"n",
      "12":"n",
      "12.1":"n",
      "15":"y",
      "16":"y",
      "17":"y",
      "18":"y",
      "19":"y",
      "20":"y",
      "21":"y",
      "22":"y",
      "23":"y",
      "24":"y",
      "25":"y",
      "26":"y",
      "27":"y",
      "28":"y",
      "29":"y",
      "30":"y",
      "31":"y",
      "32":"y",
      "33":"y",
      "34":"y",
      "35":"y",
      "36":"y",
      "37":"y",
      "38":"y",
      "39":"y",
      "40":"y",
      "41":"y",
      "42":"y",
      "43":"y",
      "44":"y",
      "45":"y",
      "46":"y",
      "47":"y",
      "48":"y",
      "49":"y",
      "50":"y",
      "51":"y",
      "52":"y",
      "53":"y",
      "54":"y",
      "55":"y",
      "56":"y",
      "57":"y",
      "58":"y",
      "60":"y",
      "62":"y"
    },
    "ios_saf":{
      "3.2":"n",
      "4.0-4.1":"n",
      "4.2-4.3":"n",
      "5.0-5.1":"y",
      "6.0-6.1":"y",
      "7.0-7.1":"y",
      "8":"y",
      "8.1-8.4":"y",
      "9.0-9.2":"y",
      "9.3":"y",
      "10.0-10.2":"y",
      "10.3":"y",
      "11.0-11.2":"y",
      "11.3-11.4":"y",
      "12.0-12.1":"y",
      "12.2-12.3":"y",
      "13":"y"
    },
    "op_mini":{
      "all":"n"
    },
    "android":{
      "2.1":"n",
      "2.2":"n",
      "2.3":"n",
      "3":"y",
      "4":"y",
      "4.1":"y",
      "4.2-4.3":"y",
      "4.4":"y",
      "4.4.3-4.4.4":"y",
      "76":"y"
    },
    "bb":{
      "7":"y",
      "10":"y"
    },
    "op_mob":{
      "10":"n",
      "11":"n",
      "11.1":"n",
      "11.5":"n",
      "12":"n",
      "12.1":"n",
      "46":"y"
    },
    "and_chr":{
      "76":"y"
    },
    "and_ff":{
      "68":"y"
    },
    "ie_mob":{
      "10":"y",
      "11":"y"
    },
    "and_uc":{
      "12.12":"y"
    },
    "samsung":{
      "4":"y",
      "5.0-5.4":"y",
      "6.2-6.4":"y",
      "7.2-7.4":"y",
      "8.2":"y",
      "9.2":"y"
    },
    "and_qq":{
      "1.2":"y"
    },
    "baidu":{
      "7.12":"y"
    },
    "kaios":{
      "2.5":"y"
    }
  },
  "notes":"",
  "notes_by_num":{
    "1":"Partial support in older IE refers to a buggy implementation (see issue).",
    "2":"Deferred scripts may run after DOMContentLoaded - https://bugzilla.mozilla.org/show_bug.cgi?id=688580"
  },
  "usage_perc_y":97.2,
  "usage_perc_a":0.26,
  "ucprefix":false,
  "parent":"",
  "keywords":"",
  "ie_id":"",
  "chrome_id":"",
  "firefox_id":"",
  "webkit_id":"",
  "shown":true
}