YAMLRocks vs strictyaml

strictyaml takes a strong position: YAML’s implicit typing and its more exotic features are footguns, so it parses only a restricted subset and makes you supply a schema to get anything other than strings. The concern is real. The remedy is heavy: strictyaml is pure Python built on ruamel.yaml, it removes large parts of YAML, it is load-only, and it is the slowest option in the field by a wide margin. YAMLRocks answers the same concern by defaulting to YAML 1.2 and offering real JSON Schema validation, without throwing away YAML or the speed.

The concern, and how YAMLRocks addresses it

strictyaml’s headline argument is the “Norway problem”: in YAML 1.1, no becomes boolean False, so a country list containing NO (Norway) silently corrupts. YAMLRocks does not have this problem, because it defaults to the YAML 1.2 core schema, where no is the string "no".

import yamlrocks

yamlrocks.loads(b"countries: [NO, SE, DK]")
# {'countries': ['NO', 'SE', 'DK']}   strings, not [False, 'SE', 'DK']

Where strictyaml removes implicit typing entirely and hands you strings, YAMLRocks gives you correct 1.2 types by default and lets you enforce a shape with JSON Schema validation that reports line-numbered errors. You get type safety without giving up numbers, booleans, or a dumper.

Feature comparison

Feature	strictyaml	YAMLRocks
Implicit `no` -> `False`	Avoided (subset)	Avoided (1.2 default)
Typed values without cast	No (strings only)	Yes (1.2 core schema)
Schema validation	Yes (own schema DSL)	Yes (JSON Schema)
Anchors/aliases	Rejected by design	Yes (preserved)
Flow style `{}` / `[]`	Rejected by design	Yes
Custom tags	Rejected by design	Yes
Dumping arbitrary data	No general dumper	Yes
Comment preservation	Yes (via ruamel)	Yes
Implementation	Pure Python (ruamel)	Rust extension
Speed (parse)	baseline	~810x faster

Speed

YAMLRocks vs strictyaml on reading: YAMLRocks is roughly three orders of magnitude faster to load.

strictyaml is built for a specific safety story, not for throughput, and it shows: it is roughly three orders of magnitude slower to load than YAMLRocks, and it has no general-purpose dumper to benchmark at all.

Operation	strictyaml	YAMLRocks	YAMLRocks is
load	~1.38 s	~1.7 ms	~810x faster
dump	no dumper	~1.0 ms	-

What strictyaml gives up

To enforce its subset, strictyaml rejects flow style, anchors and aliases, and tags outright, and it returns every leaf as a string until a schema casts it. That is a deliberate, sometimes reasonable trade for a locked-down config format you fully control. But it means strictyaml cannot read a large fraction of real-world YAML, and it cannot write YAML back out as a drop-in dumper.

YAMLRocks reads all of standard YAML 1.2, is safe by default (it never constructs arbitrary Python objects from tags), types scalars correctly, validates against a schema when you want enforcement, and round-trips with comments intact.

When to choose YAMLRocks

Choose strictyaml only if you specifically want a maximally restricted YAML dialect and are willing to pay for it in speed and in features. For everything else, safe loading, correct 1.2 types, schema-enforced validation, reading real-world YAML, round-trip editing, and speed, YAMLRocks covers the same safety goals without the sacrifices.