Gen 1 Type Chart: A Generation Changes Reference

The Gen 1 type chart

Gen 1 includes Normal, Fire, Water, Electric, Grass, Ice, Fighting, Poison, Ground, Flying, Psychic, Bug, Rock, Ghost and Dragon. Dark and Steel join the later chart; Fairy joins the Gen 6+ chart.

Read across an attacking row → to a defending column ↓. Scroll inside the table to see every type.

0× immune · ½× resisted · 1× neutral · 2× super effective

What changed after Gen 1?

Compare an attack type with a defending type. These four entries change when the same 15 types are compared across the Gen 1 and Gen 2–5 inputs:

Dark and Steel introduce additional matchups. Those are additions to the available type set, rather than changed cells in a table whose two types already existed.

The next chart-family transition changes two entries among the existing 17 types:

Fairy adds another attacking row and defending column. Consult the full inputs when a Fairy interaction is involved; the two-row table above describes existing-type changes only.

These entries come from a fixed Pokémon Showdown source revision. The source files and their checksums are listed in the downloads. They were checked against the 838 cells across our three input tables. This is a source-consistency check, not a cartridge test.

How changes reach a dual-type result

In this disclosed model, multiply the attacking type’s factor against each defending type. An immunity makes the product zero. For a single defending type, use its factor once; never square it as if the Pokémon had two copies of that type.

Consider Bug attacking Grass/Poison. In the Gen 1 input, Bug is 2× against Grass and 2× against Poison, giving 4×. In the later chart, its ½× interaction with Poison changes the product to 1×. The combination has not changed; one input factor has.

Steel/Psychic gives a different example. A Ghost attack is 2× against Psychic in both later chart families. Steel reduces that to 1× in Gen 2–5, while the Gen 6+ product is 2×. The model makes the two factors visible so that a reader can check the arithmetic.

This multiplication is deliberately a limited chart model. Move exceptions and full Gen 1 battle behavior can differ; use a game-specific simulator when that distinction matters.

What the downloadable comparison covers

The total is n + n(n−1)/2. Reversing the order of two defending types does not create a new profile. These are mathematical type sets, not counts of species or combinations actually available in a particular game.

The v1 model generates 444 profiles and 7,479 attack-versus-profile results. For fair era comparisons, the change ledger uses only attacking and defending types shared by both eras. Under that restriction, 53 profiles change from Gen 1 to Gen 2–5 and 17 from Gen 2–5 to Gen 6+. The downloadable ledger records 92 changed attack/profile cells across those two comparisons. Adding new types is reported separately.

Sources, reproduction and corrections

Version 1.0.0 · 23 October 2026 · Published by TypeChart, an independent fan tool.

The official Pokémon type chart is useful for current-game background and explicitly notes that affinity can differ by game. Our historical inputs use the pinned, MIT-licensed Showdown implementation. The source establishes the inputs; TypeChart’s enumerated profiles and comparison ledger are our own derived outputs. Neither source endorses this reference.

Download the inputs, results, change ledger, method, scope notes, source version, license and Python script from the data links below. Place the script beside charts-v1.json and run python3 reproduce-v1.py using Python 3’s standard library. No network access or additional package is required. The script regenerates the JSON results and CSV changes.

Scope and limits

This reference does not include abilities, items, weather, special move interactions, inverse battles, Terastallization or Stellar mechanics. It does not apply Pokémon GO or Trading Card Game rules. It does not model every Gen 1 bug, damage rounding, or battle message. “Gen 6+” names the pinned standard chart family, not a promise to cover every later game mechanic.

A resistance count is not a measure of competitive strength. Stats, moves, abilities, availability and a team’s actual opponents matter. No battle win rate, damage estimate or species usage claim follows from these tables.

Found a mismatch? Send a correction with the game, attack type, defending type or pair, and a source or reproducible example. Changes to inputs or methods receive a new data version and a dated correction note.

Version 1 data downloads

Each file belongs to the 23 October 2026 v1.0.0 snapshot. Keep the source license with the input data.

Methodology JSON

Enumeration method, scope and reproduction command.

Sources JSON

Source URLs, dates and what each source supports.

Full results JSON

All 444 defensive profiles and 7,479 attack/profile results.

Change ledger CSV

All 92 changed attack/profile cells between shared types.

Chart inputs JSON

The three defender-first type tables used in this comparison.

Reproduction script Python

Regenerate results and changes offline with Python 3.

Limitations JSON

Excluded mechanics and interpretation boundaries.

Showdown license TXT

MIT license retained with the source-derived inputs.

Source version JSON

Pinned upstream revision and input-file checksums.