What is the max size of localStorage values

Question

Since localStorage  currently  only supports strings as values  and in order to do that the objects need to be stringified  stored as JSON-string  before they can be stored  is there a defined limitation regarding the length of the values   Does anyone know if there is a definition which applies to all browsers

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I really like cdmckay s answer  but it does not really look good to check the size in a real time  it is just too slow  2 seconds for me   This is the improved version  which is way faster and more exact  also with an option to choose how big the error can be  default 250 000  the smaller error is - the longer the calculation is    function getLocalStorageMaxSize error      if  localStorage        var max   10   1024   1024          i   64          string1024               string                  generate a random key         testKey    size-test-    Math random   toString            minimalFound   0          error   error    25e4          fill a string with 1024 symbols   bytes         while  i--  string1024    1e16       i   max   1024          fill a string with  max  amount of symbols   bytes         while  i--  string    string1024       i   max          binary search implementation     while  i  gt  1          try           localStorage setItem testKey  string substr 0  i            localStorage removeItem testKey            if  minimalFound  lt  i - error              minimalFound   i            i   i   1 5                    else break          catch  e            localStorage removeItem testKey           i   minimalFound    i - minimalFound    2                     return minimalFound          To test   console log getLocalStorageMaxSize        takes  3s console log getLocalStorageMaxSize  1       takes 2s  but way more exact   This works dramatically faster for the standard error  also it can be much more exact when necessary

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Once I developed Chrome  desktop browser  extension and tested Local Storage real max size for this reason  My results  Ubuntu 18 04 1 LTS  64-bit  Chrome 71 0 3578 98  Official Build   64-bit  Local Storage content size 10240 KB  10 MB   More than 10240 KB usage returned me the error   Uncaught DOMException  Failed to execute  setItem  on  Storage   Setting the value of  notes  exceeded the quota   Edit on Oct 23  2020 For a Chrome extensions available chrome storage API  If you declare the  quot storage quot  permission in manifest js         quot name quot    quot My extension quot                quot permissions quot     quot storage quot               You can access it like this  chrome storage local QUOTA BYTES    5242880  in bytes

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You don t want to stringify large objects into a single localStorage entry  That would be very inefficient - the whole thing would have to be parsed and re-encoded every time some slight detail changes  Also  JSON can t handle multiple cross references within an object structure and wipes out a lot of details  e g  the constructor  non-numerical properties of arrays  what s in a sparse entry  etc    Instead  you can use Rhaboo  It stores large objects using lots of localStorage entries so you can make small changes quickly  The restored objects are much more accurate copies of the saved ones and the API is incredibly simple  E g    var store   Rhaboo persistent  Some name    store write  count   store count   store count 1   1   store write  somethingfancy       one    man    went      2   mow     went     2    mow    a    meadow                 store somethingfancy went 1  mow write 1   lawn      BTW  I wrote it

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I ve condensed a binary test into this function that I use   function getStorageTotalSize upperLimit  in bytes          var store   localStorage  testkey      test       NOTE  Test key is part of the storage    It should also be an even number of characters      var test   function   size    try   store removeItem testkey   store setItem testkey  new Array  size   1  join  0       catch   ex    return false    return true        var backup           for  var i   0  n   store length  i  lt  n    i  backup store key i     store getItem store key i        store clear        you could iterate over the items and backup first then restore later      var low   0  high   1   upperLimit    upperLimit    1024   1024   1024    2  upperTest   true      while   upperTest   test high    amp  amp  high  lt   upperLimit    low   high  high    2        if   upperTest            var half       high - low   1    2          is a faster Math floor            high -  half          while  half  gt  0  high     half      half   2      test high    1   -1           high   testkey length   high            if  high  gt   upperLimit  high    upperLimit      store removeItem testkey       for  var p in backup  store setItem p  backup p        return high   2       2 because of Unicode storage      It also backs up the contents before testing  then restores them   How it works  It doubles the size until the limit is reached or the test fails   It then stores half the distance between low and high and subtracts adds a half of the half each time  subtract on failure and add on success   honing into the proper value   upperLimit is 1GB by default  and just limits how far upwards to scan exponentially before starting the binary search   I doubt this will even need to be changed  but I m always thinking ahead      On Chrome    gt  getStorageTotalSize     gt  10485762  gt  10485762 2  gt  5242881  gt  localStorage setItem  a   new Array 5242880  join  0       works  gt  localStorage setItem  a   new Array 5242881  join  0       fails   a  takes one spot  2 bytes     IE11  Edge  and FireFox also report the same max size  10485762 bytes

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Quoting from the Wikipedia article on Web Storage      Web storage can be viewed simplistically as an improvement on cookies  providing much greater storage capacity  10 MB per origin in Google Chrome https   plus google com u 0  FrancoisBeaufort posts S5Q9HqDB8bh   Mozilla Firefox  and Opera  10 MB per storage area in Internet Explorer  and better programmatic interfaces    And also quoting from a John Resig article  posted January 2007       Storage Space      It is implied that  with DOM Storage    you have considerably more storage   space than the typical user agent   limitations imposed upon Cookies    However  the amount that is provided   is not defined in the specification    nor is it meaningfully broadcast by   the user agent       If you look at the Mozilla source code   we can see that 5120KB is the default   storage size for an entire domain    This gives you considerably more space   to work with than a typical 2KB   cookie       However  the size of this storage area   can be customized by the user  so a   5MB storage area is not guaranteed    nor is it implied  and the user agent    Opera  for example  may only provide   3MB - but only time will tell

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I wrote this simple code that is testing localStorage size in bytes   https   github com gkucmierz Test-of-localStorage-limits-quota  const check   bytes   gt      try       localStorage clear        localStorage setItem  a    0  repeat bytes        localStorage clear        return true      catch e        localStorage clear        return false           Github pages   https   gkucmierz github io Test-of-localStorage-limits-quota   I have the same results on desktop chrome  opera  firefox  brave and mobile chrome which is  5Mbytes    And half smaller result in safari  2Mbytes

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Find the maximum length of a single string that can be stored in localStorage This snippet will find the maximum length of a String that can be stored in localStorage per domain    Clear localStorage for  var item in localStorage  delete localStorage item    window result   window result    document getElementById  result     result textContent    Test running         Start test   Defer running so DOM can be updated with  quot test running quot  message setTimeout function             Variables     var low   0          high   2e9          half         Two billion may be a little low as a starting point  so increase if necessary     while  canStore high   high    2          Keep refining until low and high are equal     while  low     high            half   Math floor  high - low    2   low              Check if we can t scale down any further         if  low     half    high     half                console info low  high  half                 Set low to the maximum possible amount that can be stored              low   canStore high    high   low              high   low              break                        Check if the maximum storage is no higher than half         if  storageMaxBetween low  half                 high   half                The only other possibility is that it s higher than half but not higher than  quot high quot            else               low   half   1                          Show the result we found      result innerHTML    The maximum length of a string that can be stored in localStorage is  lt strong gt     low     lt  strong gt  characters           Functions     function canStore strLen            try               delete localStorage foo              localStorage foo   Array strLen   1  join  A                return true            catch  ex                return false                        function storageMaxBetween low  high            return canStore low   amp  amp   canStore high             0     lt h1 gt LocalStorage single value max length test lt  h1 gt    lt div id  result  gt Please enable JavaScript lt  div gt   Note that the length of a string is limited in JavaScript  if you want to view the maximum amount of data that can be stored in localStorage when not limited to a single string  you can use the code in this answer  Edit  Stack Snippets don t support localStorage  so here is a link to JSFiddle  Results Chrome  45 0 2454 101   5242878 characters Firefox  40 0 1   5242883 characters Internet Explorer  11 0 9600 18036   16386 122066 122070 characters I get different results on each run in Internet Explorer

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I m doing the following      getLocalStorageSizeLimit   function           var maxLength   Math pow 2 24       var preLength   0      var hugeString    0       var testString      var keyName    testingLengthKey          2 24   16777216 should be enough to all browsers     testString    new Array Math pow 2  24    join  X         while  maxLength     preLength            try                localStorage setItem keyName  testString                preLength   testString length              maxLength   Math ceil preLength     hugeString length - preLength    2                 testString   hugeString substr 0  maxLength             catch  e                hugeString   testString               maxLength   Math floor testString length -  testString length - preLength    2               testString   hugeString substr 0  maxLength                        localStorage removeItem keyName        maxLength   JSON stringify this storageObject  length   maxLength   keyName length - 2       return maxLength

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You can use the following code in modern browsers to efficiently check the storage quota  total  amp  used  in real-time   if   storage  in navigator  amp  amp   estimate  in navigator storage            navigator storage estimate                then estimate   gt                    console log  Usage  in Bytes      estimate usage                                  Total Quota  in Bytes      estimate quota

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Actually Opera doesn t have 5MB limit  It offers to increase limit as applications requires more  User can even choose  Unlimited storage  for a domain    You can easily test localStorage limits quota yourself

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Don t assume 5MB is available - localStorage capacity varies by browser  with 2 5MB  5MB and unlimited being the most common values  Source  http   dev-test nemikor com web-storage support-test

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Here s a straightforward script for finding out the limit   if  localStorage  amp  amp   localStorage getItem  size          var i   0      try              Test up to 10 MB         for  i   250  i  lt   10000  i    250                localStorage setItem  test   new Array  i   1024    1  join  a                     catch  e            localStorage removeItem  test            localStorage setItem  size   i - 250                         Here s the gist  JSFiddle and blog post    The script will test setting increasingly larger strings of text until the browser throws and exception  At that point it   ll clear out the test data and set a size key in localStorage storing the size in kilobytes

[javascript] What is the max size of localStorage values?

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