diff --git a/FU/Benchmarks.pod b/FU/Benchmarks.pod
index 7366387..8f5aa73 100644
--- a/FU/Benchmarks.pod
+++ b/FU/Benchmarks.pod
@@ -104,6 +104,22 @@ String escaping (many)
           JSON::XS    154280/s
           FU::Util    132514/s
 
+Canonical hash key ordering (small)
+
+          JSON::PP       835/s
+  Cpanel::JSON::XS     28155/s
+        JSON::SIMD     30066/s
+          JSON::XS     32151/s
+          FU::Util     27079/s
+
+Canonical hash key ordering (large)
+
+          JSON::PP       756/s
+  Cpanel::JSON::XS     10710/s
+        JSON::SIMD     12640/s
+          JSON::XS     12858/s
+          FU::Util     12819/s
+
 
 
 =cut
@@ -114,6 +130,16 @@ jsonfmt/api	FU::Util	FU	0.1	129117
 jsonfmt/api	JSON::PP	JSON::PP	4.16	5342
 jsonfmt/api	JSON::SIMD	JSON::SIMD	1.06	128161
 jsonfmt/api	JSON::XS	JSON::XS	4.03	130434
+jsonfmt/canonl	Cpanel::JSON::XS	Cpanel::JSON::XS	4.38	10710
+jsonfmt/canonl	FU::Util	FU	0.1	12819
+jsonfmt/canonl	JSON::PP	JSON::PP	4.16	756
+jsonfmt/canonl	JSON::SIMD	JSON::SIMD	1.06	12640
+jsonfmt/canonl	JSON::XS	JSON::XS	4.03	12858
+jsonfmt/canons	Cpanel::JSON::XS	Cpanel::JSON::XS	4.38	28155
+jsonfmt/canons	FU::Util	FU	0.1	27079
+jsonfmt/canons	JSON::PP	JSON::PP	4.16	835
+jsonfmt/canons	JSON::SIMD	JSON::SIMD	1.06	30066
+jsonfmt/canons	JSON::XS	JSON::XS	4.03	32151
 jsonfmt/intl	Cpanel::JSON::XS	Cpanel::JSON::XS	4.38	29299
 jsonfmt/intl	FU::Util	FU	0.1	114084
 jsonfmt/intl	JSON::PP	JSON::PP	4.16	2208
diff --git a/FU/Util.pod b/FU/Util.pod
index dbf5055..fd6bb5e 100644
--- a/FU/Util.pod
+++ b/FU/Util.pod
@@ -49,6 +49,11 @@ The following C<%options> are supported:
 
 =over
 
+=item canonical
+
+When set to a true value, write hash keys in deterministic (sorted) order. This
+option currently has no effect on tied hashes.
+
 =item utf8
 
 When set to a true value, returns a UTF-8 encoded byte string instead of a Perl
diff --git a/bench.PL b/bench.PL
index 5a8b236..dbc9935 100755
--- a/bench.PL
+++ b/bench.PL
@@ -65,20 +65,28 @@ sub def($id, $text, @f) {
 
 
 
-# Use similar options for fair comparisons.
-my $j_cp = Cpanel::JSON::XS->new->allow_nonref->unblessed_bool->convert_blessed;
-my $j_pp = JSON::PP->new->allow_nonref->core_bools->convert_blessed;
-my $j_xs = JSON::XS->new->allow_nonref->boolean_values([false,true])->convert_blessed;
-my $j_si = JSON::SIMD->new->allow_nonref->core_bools->convert_blessed;
 use FU::Util 'json_format';
 
 sub jsonfmt($name, $text, $data) {
+    # Use similar options for fair comparisons.
+    my $cp = Cpanel::JSON::XS->new->allow_nonref->unblessed_bool->convert_blessed;
+    my $pp = JSON::PP->new->allow_nonref->core_bools->convert_blessed;
+    my $xs = JSON::XS->new->allow_nonref->boolean_values([false,true])->convert_blessed;
+    my $si = JSON::SIMD->new->allow_nonref->core_bools->convert_blessed;
+    my @opt = ();
+    if ($name =~ /^canon/) {
+        $cp = $cp->canonical;
+        $pp = $pp->canonical;
+        $xs = $xs->canonical;
+        $si = $si->canonical;
+        @opt = (canonical => 1);
+    }
     def "jsonfmt/$name", $text,
-        'JSON::PP',         undef, sub { $j_pp->encode($data) },
-        'Cpanel::JSON::XS', undef, sub { $j_cp->encode($data) },
-        'JSON::SIMD',       undef, sub { $j_si->encode($data) },
-        'JSON::XS',         undef, sub { $j_xs->encode($data) },
-        'FU::Util',         'FU',  sub { json_format $data };
+        'JSON::PP',         undef, sub { $pp->encode($data) },
+        'Cpanel::JSON::XS', undef, sub { $cp->encode($data) },
+        'JSON::SIMD',       undef, sub { $si->encode($data) },
+        'JSON::XS',         undef, sub { $xs->encode($data) },
+        'FU::Util',         'FU',  sub { json_format $data, @opt };
 }
 
 # From JSON::XS POD.
@@ -94,7 +102,8 @@ jsonfmt stru => 'Unicode strings', do { use utf8;
 jsonfmt stres => 'String escaping (few)', [ map 'This string needs to "be escaped" a little bit', 1..100 ];
 jsonfmt strel => 'String escaping (many)', [ map "This \" \\ needs \b\x01\x02\x03\x04 more", 1..100 ];
 
-
+jsonfmt canons => 'Canonical hash key ordering (small)', [ map +{ map +("string$_", 1), 'a'..'f' }, 0..100 ];
+jsonfmt canonl => 'Canonical hash key ordering (large)', { map +("string$_-something", 1), 'aa'..'zz' };
 
 
 
diff --git a/c/jsonfmt.c b/c/jsonfmt.c
index 48264dc..70dfbef 100644
--- a/c/jsonfmt.c
+++ b/c/jsonfmt.c
@@ -1,6 +1,7 @@
 typedef struct {
     fustr out;
     UV depth;
+    int canon;
 } fujson_fmt_ctx;
 
 static void fujson_fmt(pTHX_ fujson_fmt_ctx *, SV *);
@@ -126,19 +127,65 @@ static void fujson_fmt_av(pTHX_ fujson_fmt_ctx *ctx, AV *av) {
     fustr_write(&ctx->out, "]", 1);
 }
 
+static int fujson_fmt_hvcmp(const void *pa, const void *pb) {
+    dTHX;
+    HE *a = *(HE **)pa;
+    HE *b = *(HE **)pb;
+    STRLEN alen, blen;
+    char *astr = HePV(a, alen);
+    char *bstr = HePV(b, blen);
+    int autf = HeUTF8(a);
+    int butf = HeUTF8(b);
+
+    if (autf == butf) {
+        int cmp = memcmp(bstr, astr, alen < blen ? alen : blen);
+        return cmp != 0 ? cmp : blen < alen ? -1 : blen == alen ? 0 : 1;
+    }
+    return autf ?  bytes_cmp_utf8((const U8*)bstr, blen, (const U8*)astr, alen)
+                : -bytes_cmp_utf8((const U8*)astr, alen, (const U8*)bstr, blen);
+}
+
+static void fujson_fmt_hvkv(pTHX_ fujson_fmt_ctx *ctx, HV *hv, HE *he, char **hestr) {
+    STRLEN helen;
+    if (*hestr) fustr_write(&ctx->out, ",", 1);
+    *hestr = HePV(he, helen);
+    fujson_fmt_str(aTHX_ ctx, *hestr, helen, HeUTF8(he));
+    fustr_write(&ctx->out, ":", 1);
+    fujson_fmt(aTHX_ ctx, UNLIKELY(SvMAGICAL(hv)) ? hv_iterval(hv, he) : HeVAL(he));
+}
+
 static void fujson_fmt_hv(pTHX_ fujson_fmt_ctx *ctx, HV *hv) {
     HE *he;
-    STRLEN helen;
     char *hestr = NULL;
 
-    hv_iterinit(hv);
+    int numkeys = hv_iterinit(hv);
     fustr_write(&ctx->out, "{", 1);
-    while ((he = hv_iternext(hv))) {
-        if (hestr) fustr_write(&ctx->out, ",", 1);
-        hestr = HePV(he, helen);
-        fujson_fmt_str(aTHX_ ctx, hestr, helen, HeUTF8(he));
-        fustr_write(&ctx->out, ":", 1);
-        fujson_fmt(aTHX_ ctx, UNLIKELY(SvMAGICAL(hv)) ? hv_iterval(hv, he) : HeVAL(he));
+
+    /* Canonical order on tied hashes is not supported. Cpanel::JSON::XS has
+     * code to deal with that case and it's absolutely horrifying. */
+    if (ctx->canon && !(SvMAGICAL(hv) && SvTIED_mg((SV*)hv, PERL_MAGIC_tied))) {
+        SAVETMPS;
+        if (numkeys < 4) numkeys = 4;
+        if (SvMAGICAL(hv)) numkeys = 32;
+
+        SV *keys_sv = sv_2mortal(newSV(numkeys * sizeof(HE*)));
+        HE **keys = (HE **)SvPVX(keys_sv);
+        int i = 0;
+
+        while ((he = hv_iternext(hv))) {
+            if (i >= numkeys) {
+                numkeys += numkeys >> 1;
+                keys = (HE **)SvGROW(keys_sv, numkeys * sizeof(HE*));
+                numkeys = SvLEN(keys_sv) / sizeof(HE*);
+            }
+            keys[i++] = he;
+        }
+        qsort(keys, i, sizeof(HE *), fujson_fmt_hvcmp);
+        while (i--) fujson_fmt_hvkv(aTHX_ ctx, hv, keys[i], &hestr);
+        FREETMPS;
+
+    } else {
+        while ((he = hv_iternext(hv))) fujson_fmt_hvkv(aTHX_ ctx, hv, he, &hestr);
     }
     fustr_write(&ctx->out, "}", 1);
 }
@@ -222,6 +269,7 @@ static SV *fujson_fmt_xs(pTHX_ I32 ax, I32 argc, SV *val) {
 
     ctx.out.maxlen = 0;
     ctx.depth = 0;
+    ctx.canon = 0;
     while (i < argc) {
         arg = SvPV_nolen(ST(i));
         i++;
@@ -229,7 +277,8 @@ static SV *fujson_fmt_xs(pTHX_ I32 ax, I32 argc, SV *val) {
         r = ST(i);
         i++;
 
-        if (strcmp(arg, "utf8") == 0) encutf8 = SvPVXtrue(r);
+        if (strcmp(arg, "canonical") == 0) ctx.canon = SvPVXtrue(r);
+        else if (strcmp(arg, "utf8") == 0) encutf8 = SvPVXtrue(r);
         else if (strcmp(arg, "max_size") == 0) ctx.out.maxlen = SvUV(r);
         else if (strcmp(arg, "max_depth") == 0) ctx.depth = SvUV(r);
         else croak("Unknown flag: '%s'", arg);
@@ -244,5 +293,4 @@ static SV *fujson_fmt_xs(pTHX_ I32 ax, I32 argc, SV *val) {
     return r;
 }
 
-/* TODO: canonical */
 /* TODO: pretty */
diff --git a/t/json_format.t b/t/json_format.t
index 03b20e7..4a5470f 100644
--- a/t/json_format.t
+++ b/t/json_format.t
@@ -44,7 +44,7 @@ my @tests = (
 
     {}, '{}',
     {'a',1}, '{"a":1}',
-    do { tie my %h, 'Tie::StdHash'; %h = ('a',1); \%h }, '{"a":1}',
+    do { tie my %h, 'Tie::StdHash'; %h = ('b',1); \%h }, '{"b":1}',
     do { tie my %h, 'MyOrderedHash', one => 1, two => undef, three => []; \%h }, '{"one":1,"two":null,"three":[]}',
 
     do { my $o = [true]; bless \$o, 'MyToJSON' }, '[1,"MyToJSON",[true]]',
@@ -68,7 +68,7 @@ my @errors = (
     do { my $o = {}; bless $o, 'MyToJSONSelf' }, qr/MyToJSONSelf::TO_JSON method returned same object as was passed instead of a new one/,
 );
 
-plan tests => @tests*2 + @errors/2 + 8;
+plan tests => @tests*2 + @errors/2 + 9;
 
 for my($in, $exp) (@tests) {
     my $out = json_format $in;
@@ -87,6 +87,10 @@ for my ($in, $exp) (@errors) {
 }
 
 
+is json_format({qw/a 1 b 2 c 3 d 4 d1 5 d11 6/, do { use utf8; qw/ü 7 月 8 💩 9/ }}, canonical => 1),
+   do { use utf8; '{"a":"1","b":"2","c":"3","d":"4","d1":"5","d11":"6","ü":"7","月":"8","💩":"9"}' };
+
+
 eval { json_format [[]], max_depth => 2 };
 like $@, qr/max_depth exceeded while formatting JSON/;