Atdhe Nuhiu had given Sheffield an early lead, thumping in a header from a corner before the midfielder came off the bench to make his first appearance since rejoining the club on loan from Crystal Palace.
The Wales international had almost put in Conor Sammon with a terrific pass just after the hour but when the ball rebounded to his feet just inside the Owls’ box, he buried a right foot strike into the net.
Williams’ night ended a few minutes early though with what looked like a possible groin injury as Town maintained a top six place.
Blues made two changes to the side that beat Rotherham at the weekend, with Cole Skuse and Teddy Bishop coming in for Paul Anderson and Kevin Bru.
Town were rocked back inside the first five minutes though, Dean Gerken palmed away Chris Maguire’s shot but from the resultant corner, Nuhiu headed in at the near post to give the Owls the lead.
Bishop came to Town’s rescue with a well timed tackle to stop Lewis Buxton making inroads down the Blues’ left as the home side started brightly, Maguire dragging a shot wide.
Luke Chambers cleared at the near post, then Wednesday had the ball in the net on 20 minutes from another corner, Nuhiu denied by Gerken with Kamil Zayatte heading the ball in but referee Darren Bond awarded a free-kick against Nuhiu.
Christophe Berra threatened at the back post from a corner, Sammon then denied by Glenn Loovens’ challenge inside the box as Town looked to get a foothold in the game.
Luke Hyam forced Keiren Westwood into his first save of the game with a right foot drive from the edge of the box on 35 minutes, Daryl Murphy inches away with a header soon after from Tyrone Mings’ cross as Blues threatened an equaliser.
Gerken went down well to smother Maguire’s shot, with Murphy responding at the other end with a header over as the half came to an end with the Owls holding on to their early goal.
David McGoldrick couldn’t control his volley as the second-half got underway, Murphy then almost finding a way through the home defence as Town started on front foot.
Nuhiu had the ball in the net again for Wednesday but not before the offside flag was raised, the Albanian frontman then denied by terrific cover work from Skuse as the Owls broke following a Town corner.
Twelve minutes into the second-half, Town made a change with Williams back in a Blues’ shirt for the first time since he lined up against Wednesday on the final day of last season, Bishop making way.
Maguire volleyed wide from the angle in another effort at goal from the midfielder but Town were level on the hour, Williams firing into the bottom corner from 15 yards then celebrating in front of the travelling Blue Army.
Sammon blasted wide after McGoldrick had found him inside the box, Maguire sending a deflected effort just wide, the midfielder then picking up a yellow card for a foul on the breaking Williams.
Town made a second change on 72 minutes, Anderson replacing Sammon, the wideman playing up front as Blues kept with a frontline of three.
Stevie May headed wide for the hosts from a good position as the game entered the last 10 minutes, Berra heading over at the other end after a free-kick from Anderson.
The draw – the third successive 1-1 result between the clubs at Hillsborough, sees Blues maintain a Play-Off place.