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'''Quality''' is a feature of the [[Space Age]] expansion, it introduces four higher quality levels for all items, structures and equipment with improved attributes. The goal of Quality is to allow vertical factory upgrading as alternative to expansion in size. Items of higher quality are created by chance when using Quality modules in the producing structure, the two highest quality tiers require technology not available on Nauvis.

== Quality tiers ==
There are 5 quality tiers in vanilla gameplay, with tier strength in brackets:
* [[File:quality_normal.png|15px]] Normal (0)
* [[File:quality_uncommon.png|15px]] Uncommon (1)
* [[File:quality_rare.png|15px]] Rare (2)
* [[File:quality_epic.png|15px]] Epic (3)
* [[File:quality_legendary.png|15px]] Legendary (5)

== Quality effects ==
The currently known effects of quality strength are as follows:
* +30% health
* +30% energy output
* +30% crafting speed
* +30% robot limit (rounded down)
* +30% robot recharge rate (both number and speed, rounded down)
* +30% positive module effects (rounded down for at least quality modules)
* +10% turret range
* +1 tile reach for power poles
* +1 equipment grid size (both dimensions)
* Larger inventory (unknown boost size)
* Increased ammo damage (30%?)
* Faster inserters
* Reduced resource depletion on miners (likely multiplicative in effect with productivity)
* Larger capacity on accumulators
* Increased output rate on nuclear reactors, boilers, and steam engines/turbines
* Reduced power consumption on beacons
* Larger scan range on radars
* +100% durability on consumable items (repair packs, science packs)

These effects are per quality strength and additive, a Legendary [[Productivity module 3]] would grant 25% productivity.

Some buildings, such as [[Transport belt]]s and [[Wall]]s, only gain increased health.

== Creating high-quality items ==

There are two ways to create an item with above normal quality: The player must either use ingredient items of the same quality, or use quality modules for a random chance of a higher-quality item.

=== Quality ingredients ===
Recipes that create items have variations for each quality that the item might take. When setting such a recipe in a production unit, an ingredient quality must be selected. For these variations, the set of ingredients required is the same, except that all item ingredients must have the specified quality.

Item ingredient quality requirements are exact, not minimum. For example, one can not combine uncommon [[iron plate]]s with rare [[battery|batteries]] to make an [[accumulator]] of any quality. One must therefore ensure that high-quality items to not clobber belts and starve production units of lower-quality items.

As fluids do not possess any quality, they are exempt from ingredient quality requirements; The same [[lubricant]] can be used to create [[electric engine unit]]s of any quality.

=== Quality modules ===
[[File:quality_module_animated.png|64px|right]]'''Quality modules''' allow crafting machines to produce items of a higher quality than their ingredients. Each module adds 1%/2%/2.5% quality chance to a machine, depending on its tier.

When working out the odds of improving quality, a machine starts with the sum of the quality chance of all its modules. When the machine produces an item, it performs a random roll with that chance to succeed. If it succeeds, the product is upgraded 1 level from its ingredients. If the product was upgraded, the machine repeats this process, now with a constant 10% chance of passing, rolling and upgrading until a roll fails.

For 10% quality chance crafting recipe with all tiers unlocked, this gives the following odds:
{|class="wikitable" style="text-align: center;"
! Input !! [[File:quality_normal.png|32px]] chance !! [[File:quality_uncommon.png|32px]] chance !! [[File:quality_rare.png|32px]] chance !! [[File:quality_epic.png|32px]] chance !! [[File:quality_legendary.png|32px]] chance
|-
| [[File:quality_normal.png|32px]] || 90% || 9% || 0.9% || 0.09% || 0.01%
|-
| [[File:quality_uncommon.png|32px]] || - || 90% || 9% || 0.9% || 0.1%
|-
| [[File:quality_rare.png|32px]] || - || - || 90% || 9% || 1%
|-
| [[File:quality_epic.png|32px]] || - || - || - || 90% || 10%
|-
| [[File:quality_legendary.png|32px]]  || - || - || - || - || 100%
|}

For 24.8% quality chance (4x[[File:quality_legendary.png|15px]]Legendary [[quality module 3]]), the odds are instead:
* 75.2% Normal
* 22.32% Uncommon (24.8% Uncommon+)
* 2.232% Rare (2.48% Rare+)
* 0.2232% Epic (0.248% Epic+)
* 0.0248% Legendary

When using quality ingredients as an input, the base quality is the quality of the recipe. You can only use items with the same quality as input.

Quality modules are only required to ''improve'' quality, crafting will always give the base quality of the used items. Additionally, the odds of improving from a given base quality is the same as improving the same number of tiers from Normal quality.

==== Optimal module usage ====
When using [[Assembling machine 3]]s with the goal of converting all input items to Legendary outputs, and feeding non-Legendary items through a [[Recycler]] with 4 quality modules (as recyclers can't take productivity modules), the optimal number of quality and productivity modules is as follows:
* If the quality modules offer less than 15% chance, use 4 quality modules
* If the quality modules offer 16% (Rare T3s) or 19% (Epic T3s), use 3 quality modules and 1 productivity module
* If the quality modules offer 25% (Legendary 3s), use 2 of each module
* If the quality modules offer ''exactly'' 15% (Legendary T2s):
** When the base quality of the inputs is Epic, use 4 quality modules
** When the base quality of the inputs is ''not'' Epic, use 3 quality modules
*** If the productivity modules offer 1.5% or less and the base quality of the inputs is Rare, use 4 quality modules and not 3

It is also more optimal to improve quality on the lead-up to the target output item due to the recycler only giving back 25% of the input items, except for cases where the chosen item has a productivity research available, in which case looping through a recycler is optimal and has no added material cost (ignoring fluids).

== Relevant Factorio Friday Facts ==
* [https://www.factorio.com/blog/post/fff-375 FFF 375 - Quality]
* [https://www.factorio.com/blog/post/fff-376 FFF 376 - Research and Technology]

== Trivia ==
* Quality is not technically exclusive to player-made entities; Though this does not occur naturally, quality is also allowed on enemies, asteroids, and even the player character.
** Some enemies with qualities above normal can even be created in regular sandbox gameplay: Big biters, behemoth biters, and big premature wriggler pentapods born from spoiled [[biter egg]]s, [[captured biter spawner]]s, and [[pentapod egg]]s inherit the quality of the spoiled items, with the latter two being possible to craft with quality modules. Furthermore, a starved captured biter spawner will retain its quality upon converting into a hostile biter spawner, with said quality even being inherited by the biters that it will spawn. Should these biters chose to expand, they may also create quality spitters and worms.

== History ==
{{history|2.0.7|
* Introduced in [[Space Age]]{{SA}} expansion.
}}