Issuer Free Writing Prospectus to

Preliminary Prospectus

Registration Statement No. 333-146064

Dated September 20, 2007

Filed pursuant to Rule 433

This term sheet to the preliminary prospectus dated September 14, 2007 should be read together with the preliminary prospectus before making a decision in connection with an investment in the notes. The information in this term sheet supersedes the information contained in the preliminary prospectus to the extent that it is inconsistent therewith. Terms used but not defined herein have the meaning ascribed to them in the preliminary prospectus.

We have filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus included in that registration statement and other documents we have filed with the SEC for more complete information about us and this offering. You may get these documents for free by visiting EDGAR on the SEC web site at www.sec.gov. Alternatively, we, Citigroup Global Markets Inc. or any other underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling toll-free 1-877-858-5407.

CONCURRENT STOCK OFFERING

Concurrently with this offering, we are offering 3,662,556 shares of our common stock (up to 4,211,939 shares if the underwriters exercise their over-allotment option in full) pursuant to a separate registration statement, prospectus and free writing prospectus. The completion of this offering and the concurrent common stock offering are each conditioned upon the concurrent completion of the other offering. We estimate that the net proceeds from our concurrent common stock offering will be approximately $295.5 million or $339.8 million if the underwriters exercise their over-allotment option in full, after deducting underwriting discounts and estimated offering expenses.

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CAPITALIZATION

The following table sets forth our cash, cash equivalents, short-term and long-term investments and current portion of our indebtedness, and our capitalization as of June 30, 2007:

This table assumes no exercise of the underwriters’ over-allotment option and should be read in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” the “Unaudited Pro Forma Combined Consolidated Condensed Financial Statements” and our financial statements, including all related notes, included or incorporated by reference in the preliminary prospectus to which this communication relates.

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The conversion rate, including any additional shares added to the conversion rate in connection with a make-whole fundamental change, will not exceed 11.8976 (which is equal to a conversion price of $84.05 per share); however, such maximum conversion rate will be appropriately adjusted for all base conversion rate adjustments (and adjustments to the incremental share factor) described under “—Anti-dilution Adjustments—Adjustment Events” in the preliminary prospectus.

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UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED FINANCIAL STATEMENTS

The unaudited pro forma combined consolidated condensed financial statements included in this free writing prospectus have been updated from those contained in the preliminary prospectus dated September 14, 2007 solely to reflect: (i) the final terms of the Convertible Debt Offering and the Common Stock Offering, as those terms are defined below; and (ii) a decrease in the pro forma amount of goodwill as of June 30, 2007 from $423,147,000 to $421,889,000.

The following unaudited pro forma combined consolidated condensed financial statements have been prepared to give effect to the acquisition by Equinix, Inc. (“Equinix” or the “Company”) of IXEurope plc (“IXEurope”) using the purchase method of accounting and the related financings to fund this acquisition with the assumptions and adjustments described in the accompanying notes to the unaudited pro forma combined consolidated condensed financial statements, as well as certain significant transactions of the Company that have occurred subsequent to June 30, 2007 consisting of (i) additional advances under the Chicago IBX Financing, (ii) the completion of the San Jose Property Acquisition and (iii) the Asia-Pacific Financing. These pro forma statements were prepared as if the acquisition and related financings and other transactions described above had been completed as of January 1, 2006 for statements of operations purposes and as of June 30, 2007 for balance sheet purposes. The combined company will operate under the Equinix name with the current management teams in place in the U.S., Europe and Asia-Pacific.

The unaudited pro forma combined consolidated condensed financial statements are presented for illustrative purposes only and are not necessarily indicative of the financial position or results of operations that would have actually been reported had the acquisition and related financings and other transactions described above occurred on January 1, 2006 for statements of operation purposes and as of June 30, 2007 for balance sheet purposes, nor is it necessarily indicative of the future financial position or results of operations of the combined company. The unaudited pro forma combined consolidated condensed financial statements include adjustments, which are based upon preliminary estimates, to reflect the allocation of the purchase price to the acquired assets and assumed liabilities of IXEurope. The final allocation of the purchase price will be determined after the completion of the acquisition and will be based upon actual net tangible and intangible assets acquired as well as liabilities assumed. The preliminary purchase price allocation for IXEurope is subject to revision as more detailed analysis is completed and additional information on the fair values of IXEurope’s assets and liabilities becomes available. Any change in the fair value of the net assets of IXEurope will change the amount of the purchase price allocable to goodwill. Additionally, changes in IXEurope’s working capital, including the results of operations from June 30, 2007 through September 14, 2007, the date the transaction was completed, will change the amount of goodwill recorded. Final purchase accounting adjustments may differ materially from the pro forma adjustments presented here.

These unaudited pro forma combined consolidated condensed financial statements are based upon the respective historical consolidated financial statements of Equinix and IXEurope, adjusted to generally accepted accounting principles in the United States of America, and should be read in conjunction with the historical consolidated financial statements of Equinix and IXEurope and related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” of Equinix and IXEurope incorporated in the prospectus by reference.

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UNAUDITED PRO FORMA COMBINED CONDENSED BALANCE SHEET

AS OF JUNE 30, 2007

(In thousands)

The accompanying notes are an integral part of these unaudited pro forma combined condensed

financial statements.

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UNAUDITED PRO FORMA COMBINED CONDENSED STATEMENT OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 31, 2006

(In thousands, except per share data)

The accompanying notes are an integral part of these unaudited pro forma combined condensed

financial statements.

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UNAUDITED PRO FORMA COMBINED CONDENSED STATEMENT OF OPERATIONS

FOR THE SIX MONTHS ENDED JUNE 30, 2007

(In thousands, except per share data)

The accompanying notes are an integral part of these unaudited pro forma combined condensed

financial statements.

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED FINANCIAL STATEMENTS

The unaudited pro forma combined consolidated condensed financial statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission.

1. BASIS OF PRO FORMA PRESENTATION

In June 2007, a wholly-owned subsidiary of the Company announced an offer to purchase all of the entire issued and to be issued share capital of IXEurope (“the IXEurope Acquisition”). Under the final terms of the IXEurope Acquisition, IXEurope shareholders will receive 140 British pence in cash for each IXEurope share valuing the share capital of IXEurope on a fully diluted basis at approximately 270,100,000 British pounds or approximately $540,632,000 (as translated using effective exchange rates at June 30, 2007); however, fully-diluted shares of IXEurope held by IXEurope’s two top officers representing 1,974,000 British pounds of the total purchase price will not be paid in cash upon closing. Instead, equity awards of the Company’s common stock with a fair value of 1,974,000 British pounds or approximately $3,951,000 (as translated using effective exchange rates at June 30, 2007) will be issued to the two top officers of IXEurope and are subject to vesting based on continuous employment through the end of 2008, as well as certain performance criteria of IXEurope (the “IXEurope Equity Compensation”). The IXEurope Equity Compensation will not be accounted for as part of the purchase price of IXEurope. Rather, the IXEurope Equity Compensation will be expensed into operations of the combined company post-acquisition as stock-based compensation over the vesting life of such awards. As a result, the actual cash purchase price for the IXEurope Acquisition is 268,126,000 British pounds or approximately $536,681,000 (also as translated using effective exchange rates at June 30, 2007). IXEurope operates data centers in the United Kingdom, France, Germany and Switzerland. The combined company will operate under the Equinix name with the current management teams in place in the U.S., Europe and Asia-Pacific. The IXEurope Acquisition will be accounted for using the purchase method of accounting in accordance with Statement of Financial Accounting Standard No. 141, “Business Combinations” (“SFAS 141”).

Although the IXEurope Acquisition closed on the morning of September 14, 2007, the Company does not have to pay the consideration for the IXEurope Acquisition until September 28, 2007. In addition, the Company will not have completed its preliminary accounting for the IXEurope Acquisition until it reports its 2007 third quarter results in the Company’s quarterly report on Form 10-Q for the quarterly period ended September 30, 2007.

In order to provide cash to fund the IXEurope Acquisition, the Company entered into the Senior Bridge Loan for a principal amount of $500,000,000 in June 2007. However, the Company does not intend to use the Senior Bridge Loan to pay for the IXEurope Acquisition. Instead, the Company intends to pay for the IXEurope Acquisition with the proceeds from a combination of (i) the sale of 3,662,556 shares of the Company’s common stock at a public offering price of $84.05 per share (the “Common Stock Offering”) and (ii) the sale of the Company’s Convertible Subordinated Notes due 2014 (the “Convertible Debt Offering”) (collectively, the “New Public Offerings”). For purposes of the pro forma results contained herein, the Company has assumed that the Senior Bridge Loan will be terminated unused (the Senior Bridge Loan and New Public Offerings are collectively referred to herein as the “IXEurope Acquisition Financings”). The completion of each offering is conditioned upon the concurrent completion of the other offering.

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

In addition to the IXEurope Acquisition and IXEurope Acquisition Financings, the pro forma results contained herein also reflect the following significant transactions of the Company that have occurred subsequent to June 30, 2007 consisting of (i) additional advances under the Chicago IBX Financing, (ii) the completion of the San Jose Property Acquisition and (iii) the Asia-Pacific Financing as more fully discussed below (collectively, the “Other Significant Subsequent Events”).

The unaudited pro forma combined consolidated condensed balance sheet as of June 30, 2007, was prepared by combining the historical unaudited consolidated condensed balance sheet data as of June 30, 2007 for Equinix and IXEurope, as adjusted to comply with generally accepted accounting principles in the United States or U.S. GAAP, as if the IXEurope Acquisition, IXEurope Acquisition Financings and Other Significant Subsequent Events had been consummated on that date. In addition to certain U.S. GAAP adjustments, certain balance sheet reclassifications have also been reflected in order to conform IXEurope’s balance sheet with the company’s balance sheet presentation. Refer to Note 2 for a discussion of these U.S. GAAP and reclassification adjustments.

The unaudited pro forma combined consolidated condensed statement of operations for the year ended December 31, 2006 and for the six months ended June 30, 2007 combines the results of operations of Equinix and IXEurope, as adjusted to comply with U.S. GAAP, as if the IXEurope Acquisition, IXEurope Acquisition Financings and Other Significant Subsequent Events had been consummated on January 1, 2006. In addition to certain U.S. GAAP adjustments, certain statements of operations reclassifications have also been reflected in order to conform with the Company’s statements of operations presentation. Refer to Note 3 for a discussion of these U.S. GAAP and reclassification adjustments.

In July and August 2007, the Company entered into forward contracts to purchase 265,156,000 British pounds at an average forward rate of 2.020007, or the equivalent of $535,617,000, to be delivered in September 2007, for purposes of hedging a portion of the purchase price of the IXEurope Acquisition (the “IXEurope Acquisition Foreign Exchange Hedge”). The Company will be accounting for these forward contracts under the Company’s current accounting policies for hedging activities as disclosed in the Company’s last annual report on Form 10-K, which are based on the provisions of SFAS No. 133, “Accounting for Derivative Instruments and Hedging Activities,” as amended. The effects of the IXEurope Acquisition Foreign Exchange Hedge have not been reflected in the pro forma statements of operations as the hedge is directly attributable to the acquisition and is non-recurring. Upon closing and completing its accounting for the IXEurope Acquisition, the Company will record a foreign exchange gain or loss in its statement of operations based on the prevailing exchange rate between U.S. dollars and British pounds on such date.

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

2. IXEUROPE BALANCE SHEET

IXEurope’s consolidated financial statements were prepared in accordance with international financial reporting standards or IFRS, which differ in certain material respects from U.S. GAAP. IXEurope also classified certain amounts differently than Equinix in their consolidated balance sheet. The following schedule summarizes the necessary material adjustments to conform the IXEurope consolidated balance sheet as of June 30, 2007 to U.S. GAAP and to reclassify certain amounts to Equinix’s basis of presentation (in thousands):

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

IXEurope’s balance sheet has been translated into U.S. dollars at the June 30, 2007 exchange rate of GBP £1.00. = USD $2.0016

The adjustments presented above to IXEurope’s balance sheet are as follows:

Under IFRS, installation costs related to installation fees charged to customers are expensed as incurred. Under U.S. GAAP, installation costs are deferred and amortized over the same period as the related installation fee revenue. The adjustment totaling £2,976,000 reflects the deferral of such installation costs.

Under IFRS, negative goodwill arising from a business combination is recognized directly in the statement of operations. Under U.S. GAAP, negative goodwill is allocated against the carrying value of the assets acquired, which in IXEurope’s case, was predominantly property and equipment. The adjustment totaling £776,000 reflects the net impact of the allocation of negative goodwill to property and equipment.

The above reflects a reclassification separating net intangible assets from goodwill in order to conform IXEurope’s balance sheet presentation to Equinix’s balance sheet presentation.

Prior to adopting IFRS in 2005, IXEurope’s consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United Kingdom or U.K. GAAP. Under IFRS, IXEurope accounts for all business combinations by applying the acquisition method. In respect of business combinations that have occurred since January 1, 2004, goodwill represents the difference between the cost of the acquisition and the fair value of the net identifiable assets acquired. IXEurope elected not to apply IFRS 3, “Business Combinations”, to business combinations that were recognized on or before January 1, 2004. As a result, the carrying value of purchased goodwill recognized under U.K. GAAP was treated as a deemed cost upon the transition to IFRS. Under U.K. GAAP, goodwill arising from acquisitions was capitalized and amortized over the period of its expected useful life of ten years. Goodwill is no longer amortized since the transition to IFRS but is

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

tested annually for impairment. Under U.S. GAAP, goodwill ceased to be an amortizable asset effective January 1, 2002. Therefore, there is a difference between U.S. GAAP and U.K. GAAP in accounting for the amortization of goodwill prior to IXEurope’s adoption of IFRS, resulting in higher carrying values for goodwill under U.S. GAAP compared to IFRS. This increase in goodwill is offset by another IFRS to U.S. GAAP adjustment relating to the benefit of pre-acquisition tax losses carry-forward positions that are recognized subsequently and adjusted against the historically recognized goodwill, then intangible assets and finally reduce income tax expenses. The above adjustment totaling £268,000 represents the net adjustment to goodwill under U.S. GAAP.

The U.S. GAAP restricted cash and deferred tax asset reclassification adjustments are described above.

The accrued property and equipment reclassification adjustment is made to conform IXEurope’s balance sheet presentation to Equinix’s balance sheet presentation by presenting this liability separately.

The other liabilities reclassification adjustment is made to conform IXEurope’s balance sheet presentation to Equinix’s balance sheet presentation by presenting these liabilities within other current and non-current liabilities.

The stock options U.S. GAAP adjustment reverses a liability accrued under IFRS as a liability for payroll taxes which is not recognized under U.S. GAAP until it is crystallized, which is typically when the stock option is exercised.

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

The other liabilities reclassification adjustment is made to conform IXEurope’s balance sheet presentation to Equinix’s balance sheet presentation by presenting these various other liabilities (noted in notes viii and xv) within other current liabilities.

Under IFRS, installation revenue related to installation fees is recognized upon completion of the installation and acceptance by the customer. Under U.S. GAAP, installation revenue is deferred and amortized into revenue over the longer of the contract period or the estimated customer life. The installation revenue U.S. GAAP adjustment totaling £562,000 represents the current portion of this deferred installation revenue.

The U.S. GAAP debt issuance cost and capital lease obligation reclassification adjustments are described above.

The installation revenue U.S. GAAP adjustment totaling £3,670,000 represents the non-current portion of this deferred installation revenue adjustment described above.

The provisions and other liabilities reclassification adjustments are described above.

The stock options, business combination and installation revenue and cost U.S. GAAP adjustments are described above. These amounts represent the net impact of such adjustments to stockholders’ equity.

The valuation allowance for deferred tax on U.S. GAAP adjustments represents the cumulative impact of the various U.S. GAAP adjustments.

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NOTES TO UNAUDITED PRO FORMA COMBINED CONSOLIDATED CONDENSED

FINANCIAL STATEMENTS (continued)

3. IXEUROPE STATEMENTS OF OPERATION

IXEurope’s consolidated financial statements were prepared in accordance with IFRS, which differ in certain material respects from U.S. GAAP. IXEurope also classified certain amounts differently than Equinix in their consolidated statements of operations. The following schedule summarizes the necessary material adjustments to conform the IXEurope consolidated statements of operations for the year ended December 31, 2006 and the six months ended June 30, 2007 to U.S. GAAP and to reclassify certain amounts to Equinix’s basis of presentation (in thousands):