This post is meant to archive the tiering history of RBY's Lower Tiers. Bans/Unbans, Suspect Tests, Viability Ranking Updates, and Rises/Drops into each tier are included.
Note on RBY UU Viability Rankings: Prior to August 2021 update, RBY UU viability ranking updates happened frequently with only a few Pokemon rising/dropping each time. These updates will not be listed UNLESS it affects the tier below.
Color Coding:
Red - Bans/Suspect Tests
Blue - Unbans/Suspect Tests
Green - Viability Ranking Update
Yellow - Rises/Drops
RBY UU 
September 28, 2011: UUBL is deleted, creating modern RBY UU.
July 9, 2015: Rhydon drops to UU.
August 6, 2015: Moltres and Articuno are banned.
August 6, 2015: Post-Moltres and Articuno Ban Viability Rankings
September 26, 2017: Rhydon rises to OU, Dragonite drops to UU
October 8, 2017: Post-Rhydon rise/Dragonite drop Viability Rankings
December 11, 2017: Moltres and Articuno are unbanned
May 12, 2019: Victreebel rises to OU, Golem drops to UU
January 2, 2021: VR Update. Golem drops to NU.
March 8, 2021: VR Update. Venusaur Rises to UU, Poliwrath and Raichu drop to NU.
June 13, 2021: Dragonite is Suspect Tested and remain legal.
Aug 2, 2021: VR Update. Aerodactyl and Dewgong rise to UU.
June 19, 2022: Agility + Partial Trapping is banned.
June 23, 2022: Slowbro, Lapras, and Victreebel drop to UU.
June 23, 2022: Slowbro and Lapras are quickbanned.
July 17, 2022: Slowbro rises to OU.
September 9, 2022: Sleep is banned.
November 27, 2022: Lapras is unbanned.
May 15, 2023: Lapras and Hypno are banned.
June 2, 2023: Unofficial VR of "Lapras + Hypno" meta.
December 27, 2023: Sleep is unbanned.
February 4, 2024: VR Update. Golem, Clefable, Electrode, Raichu, and Ninetales rise to UU. Aerodactyl, Venusaur, and Victreebel drop to NU.
May 16, 2024: Victreebel rises to OU.
July 23, 2024: Articuno is banned.
April 1, 2025: Lapras, Hypno, and Articuno are unbanned.
June 24, 2025: Slowbro and Victreebel drop to UU. Victreebel drops straight to NU due to being in NU previously.
July 15, 2025: Partial trapping is banned.
September 23, 2025: Confuse Ray and Supersonic are banned.
RBY NU 
August 16, 2020: NU enters pre-alpha.
August 16, 2020: Golduck is quickbanned.
August 16, 2020: An initial unofficial VR is created.
January 2, 2021: Golem drops to NU.
March 8, 2021: Venusaur rises to UU, Poliwrath and Raichu drop to NU.
March 16, 2021: A post-drop VR is created.
April 2, 2021: Poliwrath is banned.
April 27, 2021: Raichu is banned.
May 21, 2021: VR update post-Poliwrath/Raichu bans.
Aug 2, 2021: Aerodactyl and Dewgong rise to UU.
April 10, 2022: First official VR is created.
January 28, 2023: Poliwhirl is banned.
April 9, 2023: VR Update, Electrode rises to NU, Porygon drops to PU.
February 4, 2024: Golem, Clefable, Electrode, Raichu, and Ninetales rise to UU. Aerodactyl, Venusaur, and Victreebel drop to NU.
February 5, 2024: Golduck, Poliwhirl, and Poliwrath are unbanned.
May 16, 2024: Victreebel rises to OU.
December 29, 2024: VR Update. Arcanine, Fearow, and Magneton rise to NU. Golduck, Nidoking, Venusaur, Exeggcute, Wigglytuff, and Kingler drop to PU.
March 26, 2025: Agility + Partial Trapping is transitively banned.
June 24, 2025: Victreebel drops to NU.
July 15, 2025: Partial trapping is transitively banned.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.
RBY PU 
April 12, 2022: PU thread is established.
July 24, 2022: An initial unofficial VR is created.
January 26, 2023: First official VR is created. Gastly rises to PU, Arcanine, Magmar, Sandslash, Electrode, Slowpoke, Poliwag, and Vileplume drop to ZU.
April 9, 2023: Electrode rises to NU, Porygon drops to PU.
December 12, 2023: VR Update. Arcanine, Scyther, Vileplume, and Magmar rise to PU. Abra drops to ZU.
April 8, 2024: Arcanine and Fearow are suspect tested and remain legal.
December 15, 2024: VR Update. Abra rises to PU, Magmar, Dragonair, Drowzee, Scyther, and Omanyte drop to PU.
December 29, 2024: Arcanine, Fearow, and Magneton rise to NU. Golduck, Nidoking, Venusaur, Exeggcute, Wigglytuff, and Kingler drop to PU.
March 26, 2025: Agility + Partial Trapping is transitively banned.
June 30, 2025: Rapidash is banned.
July 15, 2025: Partial trapping is transitively banned.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.
RBY ZU 
August 4, 2022: ZU enters Pre-Pre Alpha stage.
January 26, 2023: Gastly rises to PU, Arcanine, Magmar, Sandslash, Electrode, Slowpoke, Poliwag, and Vileplume drop to ZU.
March 4, 2023:Arcanine and Sandslash are banned. Poliwag and Slowpoke are suspected but remain legal.
April 9, 2023: Electrode rises to NU.
December 12, 2023: Arcanine, Scyther, Vileplume, and Magmar rise to PU. Abra drops to ZU.
December 12, 2023: Sandslash is unbanned.
December 12, 2023: An initial unofficial VR is created.
April 2, 2024: Arbok is banned.
April 15, 2024: VR Update.
December 15, 2024: Abra rises to PU, Magmar, Dragonair, Drowzee, Scyther, and Omanyte drop to PU.
December 15: 2024: Partial Trapping is banned.
December 15: 2024: Arbok is unbanned.
December 29, 2024: Magneton rises to NU.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.
Note on RBY UU Viability Rankings: Prior to August 2021 update, RBY UU viability ranking updates happened frequently with only a few Pokemon rising/dropping each time. These updates will not be listed UNLESS it affects the tier below.
Color Coding:
Red - Bans/Suspect Tests
Blue - Unbans/Suspect Tests
Green - Viability Ranking Update
Yellow - Rises/Drops
RBY UU September 28, 2011: UUBL is deleted, creating modern RBY UU.
July 9, 2015: Rhydon drops to UU.
August 6, 2015: Moltres and Articuno are banned.
August 6, 2015: Post-Moltres and Articuno Ban Viability Rankings
September 26, 2017: Rhydon rises to OU, Dragonite drops to UU
October 8, 2017: Post-Rhydon rise/Dragonite drop Viability Rankings
December 11, 2017: Moltres and Articuno are unbanned
May 12, 2019: Victreebel rises to OU, Golem drops to UU
January 2, 2021: VR Update. Golem drops to NU.
March 8, 2021: VR Update. Venusaur Rises to UU, Poliwrath and Raichu drop to NU.
June 13, 2021: Dragonite is Suspect Tested and remain legal.
Aug 2, 2021: VR Update. Aerodactyl and Dewgong rise to UU.
June 19, 2022: Agility + Partial Trapping is banned.
June 23, 2022: Slowbro, Lapras, and Victreebel drop to UU.
June 23, 2022: Slowbro and Lapras are quickbanned.
July 17, 2022: Slowbro rises to OU.
September 9, 2022: Sleep is banned.
November 27, 2022: Lapras is unbanned.
May 15, 2023: Lapras and Hypno are banned.
June 2, 2023: Unofficial VR of "Lapras + Hypno" meta.
December 27, 2023: Sleep is unbanned.
February 4, 2024: VR Update. Golem, Clefable, Electrode, Raichu, and Ninetales rise to UU. Aerodactyl, Venusaur, and Victreebel drop to NU.
May 16, 2024: Victreebel rises to OU.
July 23, 2024: Articuno is banned.
April 1, 2025: Lapras, Hypno, and Articuno are unbanned.
June 24, 2025: Slowbro and Victreebel drop to UU. Victreebel drops straight to NU due to being in NU previously.
July 15, 2025: Partial trapping is banned.
September 23, 2025: Confuse Ray and Supersonic are banned.
RBY NU August 16, 2020: NU enters pre-alpha.
August 16, 2020: Golduck is quickbanned.
August 16, 2020: An initial unofficial VR is created.
January 2, 2021: Golem drops to NU.
March 8, 2021: Venusaur rises to UU, Poliwrath and Raichu drop to NU.
March 16, 2021: A post-drop VR is created.
April 2, 2021: Poliwrath is banned.
April 27, 2021: Raichu is banned.
May 21, 2021: VR update post-Poliwrath/Raichu bans.
Aug 2, 2021: Aerodactyl and Dewgong rise to UU.
April 10, 2022: First official VR is created.
January 28, 2023: Poliwhirl is banned.
April 9, 2023: VR Update, Electrode rises to NU, Porygon drops to PU.
February 4, 2024: Golem, Clefable, Electrode, Raichu, and Ninetales rise to UU. Aerodactyl, Venusaur, and Victreebel drop to NU.
February 5, 2024: Golduck, Poliwhirl, and Poliwrath are unbanned.
May 16, 2024: Victreebel rises to OU.
December 29, 2024: VR Update. Arcanine, Fearow, and Magneton rise to NU. Golduck, Nidoking, Venusaur, Exeggcute, Wigglytuff, and Kingler drop to PU.
March 26, 2025: Agility + Partial Trapping is transitively banned.
June 24, 2025: Victreebel drops to NU.
July 15, 2025: Partial trapping is transitively banned.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.
RBY PU April 12, 2022: PU thread is established.
July 24, 2022: An initial unofficial VR is created.
January 26, 2023: First official VR is created. Gastly rises to PU, Arcanine, Magmar, Sandslash, Electrode, Slowpoke, Poliwag, and Vileplume drop to ZU.
April 9, 2023: Electrode rises to NU, Porygon drops to PU.
December 12, 2023: VR Update. Arcanine, Scyther, Vileplume, and Magmar rise to PU. Abra drops to ZU.
April 8, 2024: Arcanine and Fearow are suspect tested and remain legal.
December 15, 2024: VR Update. Abra rises to PU, Magmar, Dragonair, Drowzee, Scyther, and Omanyte drop to PU.
December 29, 2024: Arcanine, Fearow, and Magneton rise to NU. Golduck, Nidoking, Venusaur, Exeggcute, Wigglytuff, and Kingler drop to PU.
March 26, 2025: Agility + Partial Trapping is transitively banned.
June 30, 2025: Rapidash is banned.
July 15, 2025: Partial trapping is transitively banned.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.
RBY ZU August 4, 2022: ZU enters Pre-Pre Alpha stage.
January 26, 2023: Gastly rises to PU, Arcanine, Magmar, Sandslash, Electrode, Slowpoke, Poliwag, and Vileplume drop to ZU.
March 4, 2023:Arcanine and Sandslash are banned. Poliwag and Slowpoke are suspected but remain legal.
April 9, 2023: Electrode rises to NU.
December 12, 2023: Arcanine, Scyther, Vileplume, and Magmar rise to PU. Abra drops to ZU.
December 12, 2023: Sandslash is unbanned.
December 12, 2023: An initial unofficial VR is created.
April 2, 2024: Arbok is banned.
April 15, 2024: VR Update.
December 15, 2024: Abra rises to PU, Magmar, Dragonair, Drowzee, Scyther, and Omanyte drop to PU.
December 15: 2024: Partial Trapping is banned.
December 15: 2024: Arbok is unbanned.
December 29, 2024: Magneton rises to NU.
September 23, 2025: Confuse Ray and Supersonic are transitively banned.