Why Is CORNING INC (GLW) Stock Down Today?

Corning Inc (GLW) fell 15.33% to $121.39 in a volatile session driven by a disappointing guidance update and a broader sell-off in optical stocks. The stock opened with a -4.1% gap from the previous close and continued to decline throughout the morning, reaching an intraday low of $114.50. The move followed the company’s Q2 earnings report, which, while beating estimates, included a weaker-than-expected Q3 outlook that triggered a sharp reaction from investors.

What Happened

Corning reported adjusted earnings per share of $0.78 for Q2 2026, exceeding the $0.76 estimate. Revenue came in at $4.738 billion, above the $4.608 billion forecast. However, the company’s Q3 guidance for adjusted EPS of $0.85 to $0.89 and revenue of $4.9 billion to $5 billion fell short of expectations, particularly in the optical fiber segment, where growth is slowing. The guidance update led to a sharp sell-off, with the stock tumbling more than 16% in early trading. The move triggered a broader decline in optical stocks, with companies like Marvell, Lumentum, AXT, and Coherent also seeing double-digit losses.

What The Data Shows

The session was marked by high volatility and heavy trading, with 23.1 million shares exchanged, 1.7 times the 3-month daily average. The stock opened at $137.47 and hit a high of $144.17 before declining sharply. The price action reflects a broader 30-day trend of declining sentiment, with the 7-day average at 49/100, down from 53/100. Over the last 8 sessions, the stock has fallen 11.6% from $162.13 to $143.36. Recent insider transactions also show a pattern of selling, with seven insiders collectively offloading $36.7 million in shares over the last 90 days. Additionally, unusual options activity saw a notable call premium of $8.4 million, with no put activity reported.

What To Watch

Corning’s next key event is its scheduled Q3 earnings report, which will provide further insight into the company’s performance in the optical fiber and display segments. Investors will also monitor the breadth of coverage and sentiment shifts in the coming days, as well as any follow-up guidance from management.