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I don't know what we call this. but i found a image at google 404

url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAKsAAADVCAMAAAAfHvCaAAAAGFBMVEVYn%2BH%2F%2F%2F%2Bex%2B3U5vd7s%2Bfq8%2Fs0itq72PMLUPvtAAASvklEQVR4AbXBC0JqCQxEwT5Jd7L%2FHc8FdR4g%2BEGtEr8u%2FBHxu7otdzd%2FQPyqlmRp1Pw%2B8aukDfRa1fw28ZtWy4sa89vEb7LCi0zx28RvqgkvouW3id%2FU8pbtWmv5beJXRWNrRmp%2BnfhlHXZm%2BQPi95Vk%2FoD4fZbMHxC%2FryTzB8Tva435A%2BL3rcb8AfH7VjJ%2FQPy%2BHYk%2FIH5facwfEL8iaZcrnKyn%2BAPi57K2VL2WF1hJ%2FAHxQ2tJrg6HteXVjPkD4ge6V3J1%2BF97zhx%2BnXhWb8nacKXlnYPErxNPyfqw4ZYKVuUZdfhd4hmxunY73NICgfWMOvwm8ZQ1pMvlDZdaCic98kjV4beIp8ScpLvsSvhflzqQmqVLB281v0E8pc2bdNne8EayNTPNSbt02PBj4intcKltb%2FNibY%2BLf9aSO%2FyMeMo6XMva3g0vwrWsxvyMeEoc3knZ2g53ZaXa8DzxlHa4J23Jae5aycXTxFPa4WRdXAtdsivckZXG4TniKWtOSlre6y7LG651Wxq5OzxDPGUVIKNwX6ekCv%2B0ddglVPMM8ZQ10FJ4LGVvOEuXRl7OqnmGeEor4Ck%2BtnI1ZEvjDa%2FcPEM8ZQVY4RO9VqUlN%2F84PEM8JQ50cUgXH2mrKlyq5RniOQ4vVjPLHdu86OKGi2eIr%2BgNV6JwljmYO6zlbJsbWp4hPtVrjYpLLV7UHIp7rOVkixtaniE%2BU5I2Nc2FKJytZhTuiac5rLnh4hniEzUbDjXhn3g5W0nNA1aAKm7YPEN8bMecrZYLWl70hkcyBay5YfMM8aHI4aR7xAUVHyirOdhAmRsqniE%2BtOKsRjIXtDzmmRGHVmDFDRfPEB%2BJzMmO01xScdYnVRs6vPHMFG9W4ZrMM8RHouWw43DNhlDWiSVZY3nDoWYc3qzDNZlniPe6w4uoOFjcKhPXuJNWyG6VqjSuhm7%2BiZorUfEM8U5J8nKyMw0tcZLwPxdRtTlUcUgVdGlml0uZ4pqKZ4hr5VUnpSXdUgVa4hA5vHERV1Tp9XhdJTWHksYd%2Ftdarql4hrjQiaPiYLclNSeebVYz5o0W7Ghsa9blmlFtx01rxP8yy5XIPEP8L1W7bjWHlbzhRTwjzXrCK1f3qqSEyBysLVtayKp40yqurcITxJtUgavVHNob%2FinZTWt5VVvWVKvJSttQCkRjb%2FA4vLK5thOeIN6sm9ai5cTFhYRDy%2FyTGpdU0hxkaZvWUrZluTmLims14QniVbywClqgeouT9IZXNWoupGzNqHa3y5LGVYBnipbCSVxcq1meIN54oRXsbEk26S3NmBcZ807K3gon2ZLcxF5tPMVJprlWE54g3nihtbRHm7WjkbxTHSCWwj1r2U4HSMmdQEmWwonNtah4gnhjA9ZSaohmpnpDjWRptDwS25LcQGsc2Bla5sTFtZV4gnixpWmIVWpgRuVwsiV5q7kv0JJcNVIFapydUrHTQKa5IfMEcRKrurSQ0qhsmVR4kea%2B7pIr9NqSrRltWlaxomUgVVyLxBPEYeUGygtszew2KfOBclVpVN2ctCXNidZaaKWmONhc6rKaJwi6xuGkRmWpAkRa7outF9XN%2F7LlmbJmpiCyvBxk%2FtnSqHmGWGk5i2ZcaWBLau5KKHt3Ce%2FsaLMz46VG4cTFm%2FaMOzxFUYWztjzhkNI43JPyYvPAegPxzFRpOYmWF1WywrPUag5xjRapqqxxubijvYFVaC%2Fv7YSDpzxjzlbhpKXxhqcpWshqtECk0Yys6m5utZdD1LCuCifhfyVOapqsxhyiQMmSm58QNdZheZGV5FqwueXiZBUga28DvRte1NQCpQVSUkFqPbIr%2FIxg7arwJqqEg6e5Vuas1Zytyw1ka5uT9ajKI87WbksaLT8mbkXFyWqaa2rOVuFVStUNpGrDoSTPmDfWdlby8kPiHQtoa0vLpXU4WzX%2FS5W2gWxtOHQ24U3CSUmu8BPinR2XVSFyuNAOZ9Fyae1qDu2qcF8suRKeJt7pcW1zaE9xwcVZq7nWtpeTrQ0PrEeq8CTxnsWrlbThELra5ixqbsXWNoeq6nBft6TlOeK9VnG2lfb4TKOOlpOouKPsWg4pb3Nf1uMGusP3iDtKDaTcgMuWvL1FmZOouCtlbwJs1Yb7SuN2Nd8k7mgvXV4OKWALiGkVJ14eyPqQQG9Vc0dWGnn5LnFPTW1z1gW0OdSyag5aHsvaroVs1YZL2dKMt1nzXeKulas52QLanGy3xq4a87Eu2yHZ2uZNWzPjDbDmu8R9a8m7iQNscbKyy%2BWS%2BUzWtqp7qzpA1jPj8KKK7xIPZG2NVWTTSbpKbs5cfEF6y64qV6ctqcKbdvgm8VhSlnWwJbuaV3LzRb11onFt%2BKcVvkl8one7u3bD%2FzJuXnRt%2BFTXVHOWqubQ4rvEEyI1L1Z2h8%2B0eRHLKiBqvkk8IePmxZq1lk%2B0w0nJUHKIlm8ST8ioeVEFtFwbPhA3h8gcdpZV803iCRkVL7Y42bK2w0NlDqXlpJRV803iGZYrnFRxlqwO3eEuN4dSOGlVme8Sz7C37QZqeZPekl0b3nMBreKsp1bNN4lnWIEtF1Vc6i1bVZtwxQX0NC9UrfBN4hk7zaHLNrey1kgVLljATnO2rmj5JvEMqzlrF%2B%2BFXitcsAArnFkdLd8knrFqPmFzyQq0xUm0tJZvEs8oAR0eix0u1ARSqg70NNHyTeIZUqgZ85gdLlgcMjOSRlBqvkk8wwOSp3moJlyoCYfeKkmBVvgm8YyaUJJ5zOJSTXMWSgus%2BC7xjJpA%2BMiquVATXiUcSuGbxDNqmk%2BUxtW82WmurMI3iWd4wifaHo1rNxx2miul8E3iGTXhc4nH0lQ1O80VK3yTeEYNX5SspbEnXFmFbxLPqGm%2BrsvWFFdK4ZvEM2rCt6RmzCWL7xLP2Anfs2M3Fyy%2BSzyjpvmqDoed5YrFd4ln7DRftHI19BRXSuGbxDN6wtdEqjF4lisS3yWeEYUvWlkDNeZKTfgm8ZFu7mqFr%2FKMYae4lFH4JvGBVLgraghf09uQMZdabr5JfKC2q1zV3IgarOLLPMWllptvEo%2B1e7dkq5ZrLkip%2BKqa4lLk5ZvEY15INay9XIqXVGS%2BqsdcirzclYVa7hAPbQFVnJSaC9HCapavqjGXIjXvbNmSxi7eE4%2BsA21OumwuSQUJX1ZjLsVabqR6t7tUlrThhnjEC%2FFy6AKbCy45zdftmEutKm5UcSgHspY7XBEPVAFVHLoCUXPFkr3hi2wutba44QDr5iyeqQ3%2FiAccqOLQDhAV17pG0jZfUuZS5OJaGYiWF%2B2ypOV%2F4q5UQZtDu4G2xK10aeTlC1bhUslciQpYh7PSQtau8ErcVYZ4gXYDcUXLe1lrvBU%2B0VoutFRcWQWo4qwdTlYSr8Q9caDMwc3BDgl3xZpRb%2FORnuVCJHNlla2oOYmLQ8q7Ll6Ie6pgDaQKSCl8IF3WqAgPrbgU2VxpV1kje2EdoOWGlsOJuKMd1g14OdjNp1YjNY%2B0m0s15kYgJVlaFxBVOETuAOK9eEELrDmUli%2Fo8oy94S4Xl2LzQGukEFU46RptQLy3BWWgHSBTvEp32eGRtjTjSriQBKLlShUPrSRcnK2qtIB4Zw3tQNRAbF5FB0vhoS57JFXzZmUtuLiy5gNlTTixlkgB8Y4byhAX0HJ4Y%2FcmWkjz0NrSaMNJ5EiNi3%2FSpPlIayqA3UBcIG5tQTuwBcQOJx3AsrSzxHJ4bKs9U5xoqWnK4U17%2BUzPFLQ4iQ3iRtxQC3gBK5xZJjOutcaSpeYjsUZqKFmGOLxIaflU1jI2ZzuLuLGuLe2yBlrLC1tdWg7ZmWal8KHeGtXG0gLLSdZyha%2BoKYdDl7WIGxpbI7lSicyLqFkH2rVZF%2BwUnymNXNu8WUkVLqSaB6IpIGWXF3Ft1UC6rRq3mhc7TRXgLS2lrKb5VEoz6nCSrtE2V6p4aMeQ8tJaxLU4nGU9o%2BXVTrMF%2BLBgjYqvSNkjL%2BDxhmut5tDb3CF1uwJoEdday6vMTHjVs7GA3g3QU8tXxZJc6Q23yhxWckPCtZW1nLgQ12KFF5Ed3pQ0U7yKp%2Fi6YM%2FI4dZOA3FRRdvhSmaWMxtxI3JzVlP8k9qsVFWdbVvTfENCjcytUoBW46XscE3DizLi1o6KQ4%2FDlZRsWSfBCt%2BSdHGrzGHFOtjFtUgNNJQR78Qjr%2BVwzV4I65SazPJzrQbKq6bl5kapU7bbRryXLo3c3LATYIfMEs3yc1bA44bScqumvJ21jLgrhHdSktNWkONR%2BLmULMnbpQm3pOWkZxHf0R7NKKykDr9iq3ptuexOuJQRZ5lCfE96K5Ct5iNpe118WQKxVeGCxnYDmUL8iUjb2%2BXmexIu9Di9XtgpxJ9wcehuOzwt1gJx4ynEM9K9tS5X7fLempP2dmnDczwjTlLYi%2FiCnHXSe9LWic9k3qvlRTltLU%2Bp2lE1sKUG8bm2DiNpNBpJu5vwwuEdLa%2FWy6p4JL27Dg%2B0pUBsQHxu67C1Vb2dpLlU5h3bG87aS0vNXWtJtip0bbjDhqgB8TkvH1g115qttnfDoW0oNe%2B1Rs0hlqVRc8cSmYP4XBUfUXHNlQ5tqzkpNaXmHVV4lVpq1NxjhYP43JqP2FwracOh7OZQDuXmRmu5sjMO75SWE%2FE5F4%2F09s5wI5abQ0rFoVxZNTes7e7wvy053NpwJj7n4kVCDt29teWypJHFOy0VJ6sN0CrK4dpakmv5pxQeEZ8rQ%2B9alnU2knyo2k64Ix4vh5I5sVNarqW3u8z%2F4mkeEZ8LrCxXtbfWu9t8qqQK0DKHVtEubrWm%2BZ9VPCS%2BJN1828oB4gqwalrFtUjNP3bzkPg7sdXAyhyssF4upWb5Z8c8Jv5QWmpgVRxUsGoulMw%2FPQqPiZ%2Fp8JGVOLQWKAW6%2BCcyF2qGD4gfibe2ead5lXEDpQAu0rv8r2WgtZxl1Twm%2Ftls1HxHK7HDjZV51VIgWmBlSeMKr%2BxseZYXq%2BUx8aY0MxrvVnUC4XNxgYtrJY15taMmNlAztd0lhxfW6MChC1rFY%2BLVjlwzKutVdfhE7xjKXEiX3CuHFzWG0lLycogUXnTtxuaws6DiMfFK09kZQ9K1VSvJ3oRHslIFWuGftdzQUoWzlYONinBILRdaC8TTYPO%2F3nBFnKxLG2um%2BKfXOrg6vBdLrvJSCm9SJpy0RtucrMRq1Zy1woUy0B4HbN60ex0uiEN0KLk1xZXs2paKW9FIqrJrzP%2Fs5k17tJz0GE%2FxohwulGElOUTmTRWl5oI4lKRRsTPhVpIdc6sl10IsFW9WXNpROPH0TkGAVnFpx5a63WSKN5HVXBKwc1btEffsNO8kvBObS5lZTnaUMXFYqbnUltwg75h%2FusMVATXleWW7qk1Xb8KLVfiKlsIlj9Sc1FhFtjITboSTlSp8QMCO5JU11bb1ZlQdIHL4iprmktWROclqGlaWmvsSPiRAIy3lcAhk05vsWgfbU3xFVFyRWTUvSqqa2S7zHEFmRikt7yS18kxxFj6yY67UbNu86U6qIApPEUSasZb7Ek0DqXh5LHa4lDFWc6kd4uUpgsiaKR6pKQ61uHmsZrmyk1ZxpQ1oeYoAzaG4ry1zsuXisVJxpeQdc60N2DxFgGckc1ePixdpHkjVjrnS0kpc6u5SwMtTBKxkybUJN3bUfCaulsMVTVvNP%2BmyNQVe7tjlE%2BJFb1mSLVfV9jaHHS2fiao15sqOd4pL29ArbxXvldV8TPwv6XVV6YXtGTefiiqaMRei2TFXKpzUONxKFWo%2BJt5J0ltlzQxfsCqimSpv86KmrHApBbXA2s2NuKPwMfFQvOELWgvsnEjVQMYtc2UXqjm0xI0yq%2FAx8T0JtyJz8DiekWpjxWoupRqqOamp5VJPsXJt9256wz3iW8oOt1xNaWah3NZJZK7UAg6HLo%2B5tFPgke2SreUe8R1rO9xayTpALFaa2Z3mUhyo4qQ6I67MbLlsyyfFPeI71m7ey0orw2pL256WuFILVHOI41mu1IyK3u0q28094nvCXQHLtqyF9Gq5tA7E4bAViRsrNW%2FCXeK3lDTVVoBI4ZIDVHFYpbTcyIbPiF%2FTSbPT3SUtl6qAuDl4W8UzxC%2Fz6CRciALUcijT4inil%2FV2p4pLtUDcwCol8xTxF8KlKg5VQGtb4jniz7UbWAcox%2BJJ4s%2B5OLiAVnuKJ4m%2FtuawBURbszxL%2FLF4OXgh9s7yNPHHqjisgVLLPE%2F8rXYD7UCrVsXzxN%2Bq4uAGrFj8gPhTXRzKwGprmh8Qf2rlot2AvSp%2BQvyl1nikAlprh58Qf0lqolGBarX8iPhLZWBVqnVsfkb8pTaHcru61PyM%2BEtrDq2UW8sPib%2FUChBvbIcfEn%2FKxWGrpeWnxJ9qVYDyVPgp8bfa2qRmmh8Tf21lq5qfE38uveE3%2FAdr385%2FSVd%2FMAAAAABJRU5ErkJggg%3D%3D") no-repeat scroll 100% 5px transparent

Does anyone know what does this mean ? what ? how? and why they serve image like that ?

Eric
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Adam Ramadhan
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4 Answers4

84

It's an inlined image (png), encoded in base64. It can make a page faster: the browser doesn't have to query the server for the image data separately, saving a round trip.

(It can also make it slower if abused: these resources are not cached, so the bytes are included in each page load.)

Mat
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    can you explain it more ? i mean how can we transfer an png to encoded in base 64 ? how part is missing :) – Adam Ramadhan Mar 09 '11 at 14:18
  • is there a maximum mb ? or something ? – Adam Ramadhan Mar 09 '11 at 14:19
  • I believe you are right that if this is used in a style sheet inside the web page it will likely not be cached on the client. This is only because most pages are dynamically served and no-cache is sent to the client. I believe if used in a .html or in the .css file it will likely be cached, dependent on your server configuration. I know I have to force refresh (clear the client cache) when I change these files on IIS. – Mike Grimm Mar 14 '16 at 19:30
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    @Mat if one wanted to eliminate the inlined image and instead have a URL to an image file (versus all the info of the image right there), how would they go about that, specifically in java script? – Anna Aug 22 '17 at 17:24
  • @Anna The only way to get a URL to an image file would be to decode the image and then upload the resulting file somewhere with a stable URL. – Michael Mior Jun 18 '21 at 14:47
18

That data:image/png;base64 URL is cool, I’ve never run into it before. The long string of characters is the base64 encoding of the actual image, i.e. no image call to the server. See RFC 2397 for details.

Side note: I have had trouble getting larger base64 images to render on IE8. I believe IE8 has a 32K limit that can be problematic for larger files. See this other StackOverflow thread for details.

Community
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Cale Sweeney
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10

That is, you are referencing an image, but instead of providing an external url, the png image data is in the url itself, embedded in the style sheet. data:image/png;base64 tells the browser that the data is inline, is a png image and is in this case base64 encoded. The encoding is needed because png images can contain bytes that are invalid inside a HTML document (or within the HTTP protocol even).

GolezTrol
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    It's not "instead of providing an URL". It's an URL with the [`data:` scheme](http://en.wikipedia.org/wiki/Data_URI_scheme). – Joachim Sauer Mar 09 '11 at 09:23
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They serve the actual image inside CSS so there will be less HTTP requests per page.

Peeter
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