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Apple dictionaries
# Thanks to commenters for providing the base of this much nicer implementation!
# Save and run with $ python
# You may need to hunt down the dictionary files yourself and change the awful path string below.
# This works for me on MacOS 10.14 Mohave
from struct import unpack
from zlib import decompress
import re
filename = '/System/Library/Assets/com_apple_MobileAsset_DictionaryServices_dictionaryOSX/9f5862030e8f00af171924ebbc23ebfd6e91af78.asset/AssetData/Oxford Dictionary of English.dictionary/Contents/Resources/'
f = open(filename, 'rb')
def gen_entry():
limit = 0x40 + unpack('i',[0]
while f.tell()<limit:
sz, = unpack('i',
buf = decompress([8:])
pos = 0
while pos < len(buf):
chunksize, = unpack('i', buf[pos:pos+4])
pos += 4
entry = buf[pos:pos+chunksize]
title ='d:title="(.*?)"', entry).group(1)
yield title, entry
pos += chunksize
for word, definition in gen_entry():
// *** Old code - not needed given the python code above
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "zlib.h"
#define CHUNK 16384
40 Length of the zlib stream
4c 0020
54 0275 number of blocks
60 808c pointer to the next block
64 8088 length of the first block
68 047a4a length of the unpacked block
6c start of the zlib stream
80fc second block
int unpack(unsigned char *in, int len)
int ret,outed=0;
unsigned have;
z_stream strm;
unsigned char out[CHUNK];
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.avail_in = 0;
strm.next_in = Z_NULL;
ret = inflateInit(&strm);
if (ret != Z_OK)
return ret;
strm.avail_in = len;
strm.next_in = in;
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = inflate(&strm, Z_NO_FLUSH);
assert(ret != Z_STREAM_ERROR); /* state not clobbered */
switch (ret) {
ret = Z_DATA_ERROR; /* and fall through */
return ret;
// printf("%lx %x\n",strm.next_in-in,strm.avail_in);
have = CHUNK - strm.avail_out /* - (outed?0:4)*/;
int off = 0;
while (have - off > 3 && out[off] != '<' && out[1+off] != 'd' && out[2+off] != ':') {
if (have - off <= 3) {
fprintf(stderr, "could not find entry\n");
if (fwrite(out + off/*+(outed?0:4)*/, have - off, 1, stdout) != 1 || ferror(stdout)) {
return Z_ERRNO;
} while (strm.avail_out == 0);
return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
char filename[256];
int main(int argc,char **argv) {
FILE *fin; int limit,blen=0,p,l,bcnt=0; unsigned char *buf=NULL;
assert(argc >= 2);
if((fin=fopen(filename,"rb"))) {
do {
// if(0==l) break;
if(blen<l) {
if(buf!=NULL) free(buf);
buf=(unsigned char *)malloc(blen);
//fprintf(stderr, "%x@%06x: %x>%06x\n",bcnt,p,l,((int *)buf)[1]);
} while(p<limit);
return 0;
// This program strips the first 4 characters from each line in the input
#include <stdio.h>
int main() {
while(!ferror(stdin) && !feof(stdin)) {
size_t len = 0;
char *line = fgetln(stdin, &len);
if (!line) break;
if (len > 4)
fwrite(line + 4, 1, len - 4, stdout);
return 0;
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vinniec commented Mar 4, 2020

Not me, I have the idea that they have changed the compression format of the dictionary entries and therefore I can't help you. At the time I tried with a Hex Editor to understand the pattern of a term, but I don't know if this tip it can help you.

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vinniec commented Mar 4, 2020

or maybe you have the same my old problem, and I can help you. In my dict the header of every compressed dict is wrongso i decompress every term only attempting a lot of time.

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Apochrosi commented Mar 5, 2020

It's this file here I have been trying to uncompress. It might be compressed a bit different than the regular dictionaries and that might be the problem.

"/System/Library/Input Methods/"

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tcardlab commented Jan 18, 2021

For those receiving "cannot use a string pattern on a bytes-like object" error, just str(entry).

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asnahu commented Mar 13, 2021

In python3, for unicode strings, should change the following lines:

title ='d:title="(.*?)"', entry).group(1) to title ='d:title="(.*?)"', entry).group(1)


print(word) to print(word.decode("UTF-8"))

it will generate correct string, if not, will get an error: cannot use a string pattern on a bytes-like object.

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jukhamil commented Jun 29, 2021

So just to be clear, we can use this script to spit out all the entries in an Apple dictionary, which we choose ourselves what format we want to save in?

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spidertwin2 commented Jul 26, 2021


I am trying to read the dictionary inside a simple react arrow function, but am a little lost with making decompression work correctly. I am stuck at the output <Buffer 00 00 00 00 ... >

If anybody has managed to make the extraction work with JS, please let me know. Thanks!


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josephg commented Sep 13, 2021

Way more up to date info here:

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