<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONDENSED CONSOLIDATED FINANCIAL STATEMENTS OF JUNO ONLINE SERVICE, INC. AND
SUBSIDIARY FOUND IN THE COMPANY'S FORM 10-Q AS OF AND FOR THE SIX MONTHS ENDED
JUNE 30, 2000 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL
STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 85,473
<SECURITIES> 0
<RECEIVABLES> 15,394
<ALLOWANCES> 1,047
<INVENTORY> 0
<CURRENT-ASSETS> 109,529
<PP&E> 16,399
<DEPRECIATION> 6,664
<TOTAL-ASSETS> 119,768
<CURRENT-LIABILITIES> 54,864
<BONDS> 0
0
0
<COMMON> 388
<OTHER-SE> 205,998
<TOTAL-LIABILITY-AND-EQUITY> 119,768
<SALES> 53,600
<TOTAL-REVENUES> 53,600
<CGS> 29,879
<TOTAL-COSTS> 29,879
<OTHER-EXPENSES> 117,570
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 91
<INCOME-PRETAX> (90,477)
<INCOME-TAX> 0
<INCOME-CONTINUING> (90,477)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (90,477)
<EPS-BASIC> (2.39)
<EPS-DILUTED> (2.39)
</TABLE>